I have several old Indiegala keys. Is it okay to make giveaways for them?

Some people claim their indiegala account got hacked, as long as the keys aren't revealed it should be fine.
Some devs could also have revoked certain games in those 2-3 years, so it's not 100% though.

In the (private) GA description repeat the explanation and ask to accept the fact that the key may not work and will not be replaced.
There are sometimes problems with leaks, not with expiration

I've run into only one revoked key (actually I recall a second one too now on a well known issue with a particular game and getting a lot of bad keys given through a bundle site itself, rather than a lapse in time, which they didn't actually replace with the real game but something I already owned and didn't want to trade...) in an actual trade out of a few hundred given out. Steam said something about it being invalid according to who(m) I was trading with, and not a duplicate. I owned the game when I tried it on my own account as well, so the key was most likely revoked, or it probably would have said that I already had the game in my library, even if the key was used.

I've had worse times with bundle sites giving me keys that were duplicates over them being revoked, so it's probably not a very common thing. I have rarely heard of it being an issue. I'd just google a particular game if I were really concerned, and if nothing comes up about bad keys or anything, then it should be fine.

Very low percentage chance. More likely to get a mixed up key or duplicate than anything else, in my experiences with things. Still, it can happen.

Has anyone had issues redeeming Indiegala keys older than 60 days?

IndieGala closed (and eventually deleted) my account when I contacted them about an overcharge on a bundle purchase, and I've heard from over a score of others who had their accounts similarly closed (and for each of us, IG refused to provide any response to our extensive attempts to communicate on the matter).

So while I can't address your specific issue ( though from what I've heard from others and seen from my own interactions prior to my account closure, getting key replacements is nearly impossible, and the only thing IG staff is good about (and surprisingly so) is offering replacements for Happy Hour glitches [which, unfortunately, appear to be relatively common] ), I can say that you should always make sure all your IG keys are backed up off-site, especially prior to contacting their support team.
Y'know- not because it's likely, given how small the overall percentage of affected IG users seems to be, but because it's possible [and really shitty when it does happen to you].

Past that, I don't believe IG keys really have a reputation for "going bad", but they do in rare occasions release dead keys that they- at least in the past- have refused to replace. So there's always a small risk, though I've not really heard of dead keys from IG for a while now, outside of those relating to issues with specific developers.

In short, you're unlikely to have problems with the keys.
As far as how to approach it with SG- they should be fine, but you're generally out on a limb by SG rules if they aren't. While simply mentioning in the description that you'd like to be able to delete if the key doesn't work can convince some non-bot-entrants to be considerate, it's generally more reliable to do an invite/group giveaway where you invite people who are aware of the circumstances beforehand. The best option is likely to offer your giveaways to an established group, with strict in-group rules about abiding by GA creator sentiments on such matters. The members of those groups aren't likely to want to burn their bridges over a giveaway they can't get a game from anyway- and generally, the members of such groups are selected for better-than-average demeanors toward the site, to begin with.

You can join Ninja Retreat Group. The Group is especially for those kind of keys. If a key won't work the winner will let you delete the GA or he gets kicked out of the group.

Just gift one of the keys to a friend and see if they are still work. You will lose one key but you will know the other works fine.

I keydropped some IG keys recently, those were over a year old - each and every single one of them was working, so there shouldn't really be a problem. Maybe search up the game's name on SG forums, just in case to avoid giving away mass revoked keys.

If it's not revealed yet and you can obtain/retrieve the key, mostly will be okay.
From my old bundles, I found some keys that invalid (maybe dev revoke unused keys) but not much, maybe only 1 or 2 keys from 15 bundles.

You can read this thread for recent Indiegala problems that faced by SG people