mine are entering their third or so month of service. i've hand washed them twice and they're still workin' like the day they arrived.
just don't use too much pressure with them and you'll be fine for a good while.
when handwashing, i will just rinse them under cold water, drop a dab of dish soap on my finger and rub it all over the sheet and then 'scrub' it good with my palms, rinse again, pat dry with a towel and let them air dry fully on a plastic cutting board or whatever is around the kitchen flipping them after an hour or two.
you'll never get everything off the sheets, it'll look like it when they're wet but after they dry you'll see some marks and stuff still. no worries though, it hasn't affected mine at all.