Sounds like bad oil seals. You can test this by driving in 2 at around 6000rpm and then letting off the gas and you should see a bunch of blue smoke behind you. This creates a large vacuum inside the engine and pulls oil through the oil seals.

 

That used to be true before turbos had water-cooled centres, but it's amazing how long the myth has continued in the 20 years since they became commonplace. There are probably more turbo timers available now than ever before! My engine's done ~185,000km/115,000miles and still has the original turbo despite never having had a turbo timer. I'm replacing it with an upgraded S5 turbo soon but it's showing no signs of age. All I've ever done to look after it is follow the instructions you'll find in the owners manual of any turbo car, and avoided hard driving for the last mile or two before shut-down.

I laughed when you said "I change the oil when I get around to it. I change the plugs when I think about it", because that sounds very familiar. I try to change the oil every 5000km and I even write the due mileage on a window sticker, but I'll sometimes miss that by a few thousand km's before I even realise. It sneaks up fast when you drive it every day. Spark plugs are definitely a "Hey it's been a while" kind of deal.