Before setting off to a punt, I've always popped a 5mg Cialis; dearer than Viagra, yes, but with no side effects and is longer lasting. I only take this for reassurance since, like a previous contributor, I don't need it when I'm with my regular partner.
On a couple of occasions, I forgot to take the thing and was shagging happily anyway! Remembered mid-shag, but finished fine.
The condom wearing doesn't interfere despite being over sixty (years, not inches), maybe because in my student days it was invariable practise to use one.