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Absolutely send them. Some people send out letters on different days of the week to see if they can get their letter in the hands of someone who will help! You have nothing to lose and a lot of points to gain, if you can get them to agree. Good luck!
It could affect you're AAoA depending on how long you've had the accounts.
A report showing one or more chargeoff accounts, paid or unpaid, can hurt for 90+ FICO points for the full time of reporting (7ish years) so your goal is DEFINITELY to get these removed. "Goodwill Saturation" method is highly recommended every month or two weeks, non-stop. http://ficoforums.myfico.com/t5/Rebuilding-Your-Credit/The-Saturation-Technique-Best-GW-adjustment-o...
Just be aware that if you get one chargeoff account deleted but there are others, you may see little to no score change based on the age of that chargeoff versus the others. So keep at it until your reports are clean, don't take no for an answer.