Questions about purchasing a used CJ tube amp

I am conversing with a guy here on Agon about purchasing his used CJ LP-70S power amp. Although the amp is very clean and seems to be taken great care of, it is possibly up to 18 years old. He states that the amp is running up to spec but has never had it into CJ or a tech to verify that and states that since they used Polystyrene coupling capacitors there is nothing to wear out except the tubes which were replaced with KT120 a year ago, supported by CJ due to the 6550 being hard to get. Not a lot of feedback on the seller and I have dealt with over zealous sellers in the past. Just looking for a little feedback from the forum before tendering an offer. Thanks