It sounds like you're doing great with them - and yes, keep hand milking and you'll have Popeye forearms.
On the subject of LONG nursers, I have a yearling Oberhasli/LaMancha doeling (who *might* be pregnant - won't know for another 6-7 weeks) who is 13 months old and STILL nursing. Drives me nuts; a big chunk of milk missing twice a day when I milk out her mamma. I can't believe that Lilly is a) still nursing, and b) Claarice still LETS her. I don't really have another pen with which to separate these two, and anyway Lilly is a *wicked* escape artist who's been known to climb straight up over fences twice her height. How long does this go on?? and isn't her drinking milk not good for the microbial balance in her rumen? Don't think for a moment she doesn't have plenty of good hay at all times, and now as spring moves along, fresh green browse. Cheeky wench!