As you say, the valve stem seals do harden and shrink over time especially if the vehicle wasn't really used for a while. Your dad has given you wise advice though, in that a catch can will not solve the underlying problem. If the stem seals are 'worn' then you would probably be leaking some oil past the seals and burning it off so they should be replaced.
Is the car burning oil? ... if so do you have an idea how much?
Until you have time to rectify the fault, it may be worth trying Forté's seal conditioner as long as the stem seals are not brittle.
https://www.forteuk.co.uk/product-detail/24/Seal-Conditioner
Again this really is a temporary solution for the stem seals but it won't solve the build up of the oily/exhaust residue in the induction manifold. It's unnecessary to remove the TB to clean it every time but worth checking it a couple of times a year with a clean once a year.
Incidentally has the car any history of new timing and balance chain kits being fitted? These are due for replacement at 100K miles or ten years whichever comes sooner.
