I like most of my SILs, but a couple of hours to chat/ have a coffee every 3 months plus holiday gatherings would be plenty for me too. I have my own life with friends, volunteering, and kids and really not that much free time, so making a few hours free to catch up every 3 months would be all I could manage.
How much time would you want her to spend with you/ what would you want the two of you to do together? For example you might love shoping but she has no money or interest in window shopping; you might love watching movies together but for her, that is a solitary activity/ she has no interest/ it is stressful because she has to get up every few minutes to check on the kids. If there is something specific you want to do with her, I would suggest you give her plenty of notice: "Hey SIL, I heard of this new museum near you, next time I am up I'd love us to go together. When would suit you?" or "I am hoping to come up sometime in March and would appreciate if you showed me how to make your famous deviled eggs, what day would be best?