emergency tyre repair

I'm in france with survival-only french so was not able to fully understand the
implications of a quick burst tyre repair I've just had carried out to get me
back to base. This particular garage was unable to find a tool to fit these
particular wheel bolts and I couldn't find one in my car kit either so he
squirted a can of gunk into the tyre and when that didn't work used an odd
looking flexible stick of something which was brutally forced into the puncture
and seems to be working. (as will be evident, I haven't a lot of experience
with this sort of thing!).
How long is a fix like this usually good for before I can next get to a properly
equipped garage and replace the wheel? The pressure seemed to be fine after 20
miles or so - what are the chances of another 20miles? Is time itself a factor
whether driving on it or not?

what have others' experiences been?
thanks