Mick, hi,
I used to ALWAYS have the green slime (as used by the army) in my cars and bikes, even have it in my wheel barrow

In MY opinion its not really worth it:
1) On my car I put a bit too much in and the balancing went out
2) I did indeed get a puncture in my car and while it MAY? have slowed it down it did still go down
3) before you can have any tyre with it repaired you gotta get it ALL washed out
4) on a POSITIVE note you should never suffer a total blowout and that on its own may warrant installing it
thats my opinion on the green slime, as for the get you home pump up can with white stuff DONT USE IT
Once you put that in its going to be a NEW tyre, they WILL NOT repair it once its in there, and if you dont let them know its in there before they crack the tyre and the stuff goes all over them they will also charge you for that too.