Batch repairs at home make sense but have a small unopened tube for roadside use.
At a puncture or two a year it would take me years to accumulate a decent batch. At that rate I'm likely to have sacrificed the tubes for bracket shim material before I get round to patching them. Which does, I suppose, makes sense.
Agreed about the custard creams, BTW. This is why they're known as "Kim biscuits" in the clarifly household.