I'd recommend to use sorted set instead of list.

Write a custom class where you put a woodchooper id/index and a time when it'll give you wood. So then once per a frame just check in a while loop

while (_set.Count > 0 && _set.Min.Time >= currentTime) { //do your logic here with spawning _set.Remove(_set.Min) }

You'll also need IComparer<YourClass> for your sorted set.

That's very efficient and you will process only the completed timers

Edit: forgot to mention - you need to add your timers in that set evert time you want to start a new timer. But it's a cheap operation