Chain - To Change or Not to Change...

[tantrumbean]

Just measured my chain on my mountain bike with the park tool thingy and it's dropping in all the way on the 0.75, still fine on the 1.0.

Now, I know in theory that indicates it's time to change the chain now, but so far it doesn't seem to cause any problems.

Would a new chain definitely work with the old cassette? I have used some gears far more than others, so worried that the new chain might end up jumping anyway...(the old one has done about 3,000 miles). Spoke to the lbs over the phone to book the bike in for a service, they said they recommend always changing cassette and chain at the same time - but that means looking at about £50 instead of £10. Problem is, they say the only way to find out if it will slip if only the chain is changed, is to go on a long ride, but with Amsterdame only 2 weeks away and the shop only open while I'm at work, I run the risk of not getting the bike back in there to get it sorted before we leave in case there is a problem (and probably end up paying another chunk of labour charges).

Just wondering if it might be cheaper to ride it into the ground completely and change cassette and change at the same time, but apparently I risk damaging the chainrings as well if I leave it too long.

I probably should be able to do all this myself, but really don't feel confident about it, plus I want to make sure the bike has been checked over professionally before setting off for 250 miles, so lbs it is and the dilemma remains.

What do you think? Change chain only and risk slippage? Change both when they might still be fine for some time and possibly pay a lot of money unnecessarily? Leave it and risk causing damage to the chainrings as well?

I'm stuck - please help!