This page gives a great overall on keeping them long term...
http://mytriops.com/articles/triops_care.stm
If you do as I said keeping the tank water parameters good and taking eggs out and dying them periodically you can keep it going forever...
If I was doing it about every four weeks I would scoop out some of the sand/gravel and let it dry out on a small china tea saucer, after it's dry (say one or two weeks) scrape off the dried up sand/gravel and eggs and return them to the tank... Repeat every 4 weeks and you should have an never ending supply of triops hatching... But, beware you will need to keep the adults fed or they will eat the new hatches...
http://mytriops.com/articles/triops_care.stm
If you do as I said keeping the tank water parameters good and taking eggs out and dying them periodically you can keep it going forever...
If I was doing it about every four weeks I would scoop out some of the sand/gravel and let it dry out on a small china tea saucer, after it's dry (say one or two weeks) scrape off the dried up sand/gravel and eggs and return them to the tank... Repeat every 4 weeks and you should have an never ending supply of triops hatching... But, beware you will need to keep the adults fed or they will eat the new hatches...