They should not be overbred. They should be given a break, since they will often only create an egg sac every couple of years, in the wild, and not every year. Breeding them too early might shorten their lifespans as well.
Creating young is extremely tough on a female animal's body - any animal - and it uses a lot of resources that can leave them more vulnerable to having health issues.
Yes.. Even if they have produced two sacs back to back, as long as she is well fed in the following months there is no reason to suspect it would do her any noticable harm over the course of her life.. Some species double "clutch" if they have the fat reserves, abundant prey or both..
When I did have females that produce multiple sacs a in one year I gave them atleast 1-2 yrs off.. I very rarely used to breed females yearly It's wise IMO to give them a year in between sacs.
I would very rarely (allmost never) try to push a female to drop another sac however but if it happened well nature ya'know. I have bred many species and still had females live out what is estimated to be a full life span in captivity.. I have also had a female drop dead after one sac.. She looked healthy so it could of been unrelated but I chocked it up to sac production.
2 sacs shouldn't effect anything lifespan wise..as pokies said, just don't breed them on back to back cycles...I like to give females a full molt cycle between pairings.
But as mentioned, breeding can come with unforeseen deaths....I had a darlingi who died in the process of dropping her sac and another that died while gravid....neither had been bred often....but these deaths are far from the norm.