When AI is in a desperate situation it'll want to form an alliance with you every turn, timer like on requests for 5 or 10 turns would be welcome

Does it costs to form an alliance? if yes, you could use it to your advantage :)

I ignore AI alliance requests.  Without fail it's an AI that's getting stomped into the curb and their goal is to drag you down with them.  They'll quickly surrender in whatever war they've been losing, costing you influence, dust, reputation and war states, opening you up to attack from (usually) the biggest, baddest Cravers on the map--which, incidentally, only helps the Cravers because now they're at war with YOU too, giving them free approval!  It's an underhanded way the game reminds you that NONE of the AI are your friends.

AI alliances are a trap.  Let the loser die while you sneak around back and pursue victory by some other path.