Around eight thousand miles ago, I had my tie rods serviced when I kept noticing a muted clumping noise coming from the driver's side front end. The problem was fixed. Yesterday, the sound returned (mysteriously, right after I topped all the tires up with correct air pressure). What kind of guarantee should I expect from the dealer, given that this work was done so recently. Or is eight months ago considered 'recent'?

Sway bar links are the most common failing suspension part on newer Volvos, not tie rod ends. Sway bar links also cause clunking whereas a tie rod end has to be pretty loose before it makes audible noise.
If you meant sway bar links instead, all Volvo parts have a 1 yr warranty.

New ones aren't any better apparently. I have an early-build 2001 V70 T5 with 60k; it's had new stabilizer links (tie rod ends) six (6) times--all covered by warranty, but what a hassle, not to mention extreme tire wear for which I am not reimbursed. Getting the attention of the agency owner has not helped. I seem to be doing better with the current set of links, after a bushing up there was found to be extremely loose! My sense is that the loose bushing somehow contributed to the failure of the tie rod ends. I, wish I could properly identify the bushing for you--it is located almost directly behind the front hubs, it's barrel shaped and can be checked by sticking a screwdriver into it and wiggling the whole assembly if it's loose. I would be sure to have this stuff checked out. I would investigate the terms of your service dept's warranty. Best wishes; hope you can save your tires.