Firstly a TS engine requires a Full Belts Service every 36K or 3 years. When I had my TS, I did the belts 40K after the last the lot and it was fine. The 72K belts change should also have seen a new water pump and a variator, along with new Rocker Gasket and replacement plugs, if they were not done on the 60K service (plugs are every 60K).
As you say, its subjective and just like any engine will all be down to the maintenance thereof. Most modern engines should easily run to 150K and beyond. The TS engine can be prone to bottom end failure if the engine has been starved of oil - you should be aware that they need regular top ups of up to 1L on average, per 1,000 miles is not uncommon. You can get a good one (like the one I had which only needed a drink every 6 months between services).
The one you mention with 94K on the clock would be due the major service at 108K, assuming it was in receipt of the 72K service change out within the time frame. The cam belt is not usually the cause of failure, it typically starts with the balancer belt going and then wrecking the engine.
If the belts were only done around 40-50K, then you need to budget circa. £500.00 - Cam Belt Kit + Balancer Belt Kit (comes with tensioners) I would also do the Aux Belt + Tensioner (as no extra labour cost) replace the Rocker Gasket, Water Pump and Variator.. possibly plugs (x8 NGK Platinum) based on the cars history and current service requirements.
I did see a Spider on Ebay that had 225K on the clock - no idea if that was original engine though, but all possible if properly maintained. My friends Audi TDI has 300K on the original engine and you wouldn't even know it.