140K Miles and considering LPG conversion

[C70Driver]

Hi,

I've had my C70 T5 (56) since new, love the car and spend a lot of time in it, I currently have 140K miles on the clock, all pretty much motorway mileage @ about 80mph.

Full service history up to about 100K then I started to service it myself every 8K miles - recently had a new timing belt and variable valve pulley fitted by Volvo - drives just like new

My question is this - how many more miles can I responsibly expect .. I'm seriously considering converting to LPG and if I think I can get another 140K would also get the clutch replaced and fix the aircon (think its the compressor / cluth - seems to be a common issue I read - got the 10-20 mins only working at about 100K) So - Is this investment worthwhile - all told, thinking about spending a few thousand pounds but will it return another 140K miles for me.

All advise appreciated - Many thanks in advance.