How long do opuntia (etc) grafts last?

[Gambel]

Hi all, young cactus enthusiast here looking for some advice.
I'm pretty much exclusively interested in outdoor cactus gardening - so because I live in Salt Lake, I'm limited to growing cold hardy cactus species.

I'm trying to get my collection off the ground, but of course buying adult plants is very expensive (and not even possible for rarer species) so I have recently been doing a ton of research on grafting as it seems it could definitely help me get some plants to adulthood faster, and may also be very helpful when trying to cultivate very fickle species (i.e. Sclerocacti).

I don't think I want to try grafting on pereskiopsis as I would ideally like to be able to just plant the grafted plants outside, which would not go very well with my winters. I've also heard that pereskiopsis grafts only last around 2-3 years and I would like the grafts to last as long as possible.

So I'm just wondering, if I graft seedlings/plants onto a hardy rootstock such as Opuntia fragilis or polyacantha (etc), how long do such grafts last? Will the fact that cold hardy cacti shrink down in the cold winter months cause a problem with the graft union? Should I just degraft once they become mature and just use the grafting to hasten growth? Or just regraft every few years?

I have no problem with simply degrafting or just regularly growing most species but my main concern is just about the few cold hardy cacti that can handle the temperatures just fine, but have very fickle root systems. If I could just graft a sclerocactus to a fragilis and then pretty much treat it like a normal hardy cactus that would be ideal. Does anyone have experience doing this kind of thing? I've already experimented with a few grafts but it's way too early to tell how my results are gonna be and I figured I would ask for advice here to figure out the best way to proceed - thanks.

[greenknight]

Never done it myself, but grafts on Opuntia are said to be very long-lasting. Here's an article on the subject: http://www.lapshin.org/cultivar/N21/graft-e.htm

[MikeInOz]

I have Opunita santa rita grafted on Opuntia ficus indica 20 years or more but I have not tried globular species.