Hi,
You can save seeds. There are varieties that are not hybrids that are slow to blot.(I'm not even sure if there are hybrids that are slow to bolt. I only know OP varieties.) Bolt tolerant is not the same as sterile. They will go to seed, just slower than normal.Heat and/or day length can affect a plants biological time clock to produce babies. So varieties that are bolt tolerant are aberrations that are not following the cues to produce seed at the proper time. They could be hybrids, but often it is a plant first noticed by a grower and seeds were saved and then grown out saving seeds of subsequent generations until a stable bolt tolerant variety is made.
So seed of an OP(Open Pollinated) bolt tolerant lettuce lets say can be saved no problem. If it were a hybrid, it is more complex. You would need time and space to make your hybrid an OP. You would save seed. Plant out the seed, rouge out plants that do not behave like you want, save seed, and do it all over again for at least 5 years.
Hope this helps,
Remy

Hi, Remy! Thank you so much! This helps alot. Thanks again! :-)