S.O.
we do it 4-5 months a year and it works really well for us. It depends on your relationship with them, and as important, your partner's relationship with them. That is one problem for us. My husband has felt like my mother becomes my co-parent when she is here with us. At those times we work to reconnect as a couple and for him as daddy too with our girls. Most of the time it's great. My mother is extremely helpful and we make a good team, whether it's in food prep or kid decisions. If you have parents with whom you share a parenting philosophy it can work, if your style is very different, it can cause huge issues. Think .... my kids never watch tv and don't eat sugar, but grandma takes it as a criticism and says what's the harm? (that's an extreme example, but you get the idea).
I suggest you give it a test run, whether it's an extended visit or some kid sharing. Really try to plan out who will do what if your family needs delegated responsibilities. Conversations about these things will avoid resentment. Really talk about whether they will do any childcare and what that will look like, who will cook meals, clean, shop. How will finances be set up, who will pay for what. ie... we love organic, but she thinks it's a waste of money... is this going to create conflict. Good luck. I think multi-generational living is a huge gift for everyone involved when it works, but it can be exhausting too, you don't want to mother a whole house of adults too.