After 28+ years in a committed relationship I haven't used a condom in decades. I can however say that getting and keeping erections doesn't get any easier with age.
IMO guys have it a lot tougher than women in this category - a woman simply needs some desire an some lubrication to successfully have a sexual encounter - even if she needs a little artificial lube - she's good to go.
However the complex mental and physical interaction necessary to get and keep an erection cannot be papered over by a little lube.
Cialis has worked for me pretty well over the past 5 years - but not so much lately. Not sure if I need a higher dose, switch to Viagra or some other solution - but like you I need to figure it out.
Getting an erection is still pretty easy - but getting distracted by helping my girl achieve her orgasm(s) or some other issue (I suppose the equivalent to putting on a condom) and poof - erection gone and difficult to regain.
If you haven't tried ED medication, that would be my first suggestion - as for me, make it a double!