Justin, thanks. Just a few points then I'll leave you to it.
Sorry I didn't mean to suggest you were in any way wrong in posting here, it is after all called 'Performance & Tuning Upgrades' and that's what you are asking about, I didn't make myself clear (often happens) I was thinking as it can be rather slow in this section and for more specific info with B6s fitted to Mk3 Octavia VRSs.
I totally agree with replacing items before they fail and before they go too far out from optimum and reasonable and reliable performance (particularly on a performance car driven in a way it was designed (hence why I have no money and car now 😄).
Many performance dampers can be "rebuilt"/"refurbed" (of course this means time off the car or two or more sets) and I expect each manufacturer has there own expected life for their different models of damper based on use of course. Things do wear as you say, oils now available cope better with things and help reduce some wear and keep things like seals in better condition for longer. Calculator out, 35k divided by 1.5, times 0.9, is (if I've pressed the right buttons) say 21k /year of rough A / B roads. +1500 Kg isn't heavy for a modern car (doesn't need 18" wheels) but isn't lightweight which is fair enough for a 5 seater road car. Depends if you are fitting the dampers yourself or paying someone else to do that and if it matters anyway. A mass market damper (like Bilstein brand name) may well be very fine and reasonably long lasting or you could perhaps look at a road sport damper from smaller British specialist companies( and perhaps adjustable dampers) which should be robust and reasonably longer lasting if only used on road driving. These things can be not as expensive as first thought and good value if more durable in performance.
Tyres, 😄 I'm more used to when 70 was low profile. You'd probably not want too higher performance tyres at 23k/year. I've seen that vid before, from another poster on here, and whilst I'm not a fan of the presenter the point is made that small variations in size won't make a big difference, particularly on modern cars with all the electronic"aids" on them, it's the design, build, make-up, composition of one tyre against another that can make more difference (hence all the tyres and associated specialist people you see at motorsports (not that I follow or particularly like motorsports).
Do bear in mind I'm not an expert in anything especially suspension and tyres but when I had the money I'd give a set of tyres 1k-miles (on road going only "sports" cars) and if I didn't like them I'd change them, what's the point of having a 'performance' vehicle (and this could be a MX-5 1.6 or 64hp a.n. other) if you can't get the performance you want (doesn't have to relate to paper figures or needles on dials or digital readouts).
Just opinions of a bloke on the internet, as always each to their own. Enjoy your car how you like to enjoy it, good luck, perhaps report back at some point and give what you actually done and how it worked out to what you wanted and needed, cheers.