It would be difficult to pin this number down precisely. Most research projects contain an incredible number of false starts, changes in direction, and obvious-in-hindsight errors, so knowing that these authors took two years to produce a paper tells you fairly little, because

• You may have more (or less) experience,
• Your subjects/specimins might be different in some subtle but important way,
• You may not need to search around for parameters that work, since they already did—or you may have to optimize something that "just works" for them.
• and so on....

However, while this information doesn't go in the paper, you can often find it out. Researchers usually have a rough idea of what their close colleagues are working on and for how long, as in "eh, it took him about a year to get those experiments going."

An even better solution is to ask! This may get you context that would be difficult to put in a paper: no one is going to write "9 months, but the postdoc is an idiot" in a paper, but they may say "only two months, but she is amazingly good at training animals; it took the new folks more like 4-5 months and even then, the behavior hasn't totally stabilized" in conversation. You don't need to know the authors well--you could email them, ask on Twitter, or even just dumb into them at a conference. People are generally happy to answer this because they either get to brag ("look how clever we are") or complain ("Yeesh, what a slog") both of which are popular conversation options. Asking may also produce an offer to collaborate, or share the actual protocols, which are probably more detailed than whatever went into the paper. So…ask!

It would be difficult to pin this number down precisely. Most research projects contain an incredible number of false starts, changes in direction, and obvious-in-hindsight errors, so knowing that these authors took two years to produce a paper tells you fairly little, because

• You may have more (or less) experience,
• Your subjects/specimens might be different in some subtle but important way,
• You may not need to search around for parameters that work, since they already did—or you may have to optimize something that "just works" for them.
• and so on....

However, while this information doesn't go in the paper, you can often find it out. Researchers usually have a rough idea of what their close colleagues are working on and for how long, as in "eh, it took him about a year to get those experiments going."

An even better solution is to ask! This may get you context that would be difficult to put in a paper: no one is going to write "9 months, but the postdoc is an idiot" in a paper, but they may say "only two months, but she is amazingly good at training animals; it took the new folks more like 4-5 months and even then, the behavior hasn't totally stabilized" in conversation. You don't need to know the authors well--you could email them, ask on Twitter, or even just bump into them at a conference. People are generally happy to answer this because they either get to brag ("look how clever we are") or complain ("Yeesh, what a slog") both of which are popular conversation options. Asking may also produce an offer to collaborate, or share the actual protocols, which are probably more detailed than whatever went into the paper. So…ask!