1st resort is always the replacement tube.
but then, for a temp fix, they work OK for me.
having a few bikes, each with their own saddle pac, I have run into having a patch kit where the rubber cement has been mostly depleted and the rest dried out... screwed...
so now I keep a few of the pre-glued patches in each kit.
done well, they'll hold for a month or even 3
but they all eventually leak.
I'll usually swap the punctured 'spare' out as soon as I get home, and if worth repairing and re-using, I'll do that at leisure, while watching a replay of a Giro stage...

BTW, I like THICKer grips on my bars ( I have long fingas...) so when I get an ultra-thin road tube which is shot, I split down the middle and use as a 'pre-wrap' on the bars. Done tight, they add just the right amount of thickness to the bars after I add the normal bar wrap on top. And it adds a nice layer of shock absorption.
works great on Vintage stuff where you might want to put cotton bar tape for the 'look'.
lota uses for old tubes...