I would suggest tackling these strategically and as soon as possible. I recently was in the exact same situation and now have 0 accounts in collections and a 740 credit score (only 15 months ago my credit score was around 580)—I would not recommend taking all your savings and paying these off (you always need some kind of emergency fund or savings for a rainy day) but I would take a small chunk and try to settle 1-2 accounts every month or so as you can. Even though it takes 7 years for these to drop off after full settlement, sometimes its worth it to wait because the longer it gets passed around to collection agencies the deeper “discount” settlement they may offer. Try to negotiate a full settlement offer for a lower amount rather than agreeing to a payment plan.
