Most tyre dealers will advise you to buy a new tyre after using any gunk or foam in the tyre. They should be looked at as an emergency measure to get you home (just like a spacesaver tyre really, except that you are limited to 50mph with a spacesaver).
If you want to hedge your bets I would have a spacesaver and the gunk, and if the punctured tyre was going to need replacing soon anyway use the gunk, otherwise use the spacesaver and get the tyre repaired asap.