For a recent position for which an offer has been made, a colleague of mine has been waiting for more than eight months for a visa to be issued. Is there any reasonable point at which it makes more sense to try to withdraw the offer (as the candidate has been unable to secure a visa, which would enable him to work) and look for a replacement? Or must the offer "stand" until a final visa decision has been made (even if there's no such date in sight, as is the case here)?
Visa issues can be seriously problematic, especially given the high degree of arbitrariness that is often applied toward people coming from disfavored countries in the developing world. For example, consider the apparently arbitrary visa denials faced by students coming to the US from Iran.
Given this I would recommend using the following criteria in making a decision:
Is the person being reasonably aggressive in acting to secure a visa? If the student is attempting to secure a visa and being blocked/slowed by outside forces, time to secure the visa should not be held against them. If the person is not bothering to act towards securing a visa, then it's the same as not bothering to physically move, and they can be let go with a clean conscience.
Is there a concrete time limit on the funds? If external requirements mean the money is on a short-term "use it or lose it" status, e.g., a 1-year externally funded project that includes a task for a postdoc, then the person may be disqualified through no fault of their own by the circumstances. In this case, I think it is appropriate to put the deadline early enough to have a reasonable chance at hiring an alternate person to fill the post. The deadline should be made clear to candidates as early as possible, however.
If the timeline can be flexed and the person is being reasonably aggressive in pursuing the visa, however, I think that it is morally important for the ideals of science to continue to extend the offer. Science should be, to the extent possible, practiced openly for the general benefit of humanity, and it needs all of the diversity of strong intellectual contributors that it can obtain, no matter where they may originate, so long as they are honest and open contributors. Giving a person time for visa issues to resolve is one small but important thing that an individual scientist can do to support that ideal.
This varies wildly between countries, and with how much you're willing to pay. A given consulate may expedite requests if paid an additional amount, but even then they are likely to include clauses about how exceptional cases may take an exceptionally long time no matter what.
You can find details on visa processing times and other visa information at the travel.state.gov site. The processing time (time to mail out the acceptance/denial) says it takes about a day if it's the US consulate in Tel Aviv; the Baghdad consulate is currently closed; and the Kabul, Afghanistan consulate takes about 33 days to arrange an appointment and then about 4 days to process.
As for the intervening time between an interview and completion of processing, meaning the time to actually make the decision, the site says the following:
These estimates do not include time required for administrative processing, which may affect a small number of applications. If necessary, this additional processing is usually resolved within 60 days of application, though some cases may take longer. When administrative processing is required, the timing will vary based on individual circumstances of each case.
Administrative Processing Information
Some visa applications require further administrative processing, which takes additional time after the visa applicant’s interview by a Consular Officer. Applicants are advised of this requirement when they apply. Most administrative processing is resolved within 60 days of the visa interview. When administrative processing is required, the timing will vary based on individual circumstances of each case. Visa applicants are reminded to apply early for their visa, well in advance of the anticipated travel date.
Important Notice: Before making inquiries about status of administrative processing, applicants or their representatives will need to wait at least 60 days from the date of interview or submission of supplemental documents, whichever is later.
About Visa Processing Wait Times – Nonimmigrant Visa Applicants
Information about nonimmigrant visa wait times for interviews and visa processing time frames are shown on this website, as well as on U.S. Embassy and Consulate websites worldwide. It should be noted that the “Wait Times for a Nonimmigrant Visa to be Processed” information by country does not include time required for administrative processing. Processing wait time also does not include the time required to return the passport to applicants, by either courier services or the local mail system.
You may be able to find additional information on expected timeframes on the website for the specific consulate.
Eight months sounds like a lot to me, but there's always the fine print that sometimes it takes a lot longer.
If you haven't already, I would request that the relevant candidate make inquiries with the consulate they applied for their visa at about the status of their application, and if there are any additional details or documents that they want.
As for withdrawing the offer and pursuing someone else, the conditions for this may be spelled out by whatever is providing the funds. Worst case, consulting with your chair or your dean (who is, ultimately, responsible for approving all hires) would be appropriate.
People have lost positions due to visa problems before. While I was doing my Ph.D. a hire from a "sensitive country" was made, but ultimately his visa was denied and the department had to scramble to find at least a lecturer to cover his teaching load.