i've also used many 20+ year old radios (many boxed for years on end) and never had to replace an electrolytic capacitor either.
i find the, if it ain't broke , don't fix it method to be very reliable, nearly as reliable as not abusing my equipment with the so called "peformance mods" in the first place.
component failure is far more common due to abuse than it ever has been due to age, although the occasional thing may blow over time whilst operating under sensible conditions, many manufacturers used borderline components that easily pop when you try to screw every last ounce of power from the final/s, not necessarily in the rf amp circuit itself.
i have to agree. the caps that were used in these vintage radios were borderline at best. with a ten volt rating they are known to go in normal use, let alone abuse. the fact of the matter is, if you want the radio to last another 20 years of normal use i would take an ounce of preventive maintainance instead of a pound of " if it aint broke.. don't fix it" in this case. ignoring the possible problems will only lead to discontent, when in fact they could have been prevented in the first place.
when you decide what shop to take it to, ask them about it. if they are a reputable shop they will tell you the same. a little more $$$ now will lessen the chance of having failures down the road. this is a fact and not my opinion. this is all out there in balck and white on the net about these issues with those vintage mobile radios, as in the grant, jackson, and cobra 148's. all one has to do is look it up.