Some of the Audi filters were kind of expensive, so when I worked on people's car who were not actually paying me, I'd reuse the filters w/o batting an eye, just drain and re-install. oem Audi filters say 30,000km/2 years on the side and re-use is commonplace in Europe.
Later, Honda recommended it, but it took a while to do so on my brand new cars. Last time around, I had a Fram TG with about 4k on it, so I re-used it even though I have a big box of new filters here.
The Astra came new with old oil in it, so it got changed at about 2k miles...do you think I NEEDED to replace the filter? I drained the oil TWICE, rinsing the outside of cartridge in the old oil stream!!!
The cartridge filters for it are $9, so I plan on using them twice per change. Yes, it got a fresh filter with the GC. I will alternate GC and M1 0w-30 SL, so I'll store the old filter in a zip lock for 6 months for reuse later with the same type oil. Don't like it? Too bad. oem service in Europe is 18k miles on those filters, 6 months is about 5k for us.
Nobody has said what harm reusing filters will cause. Not *might* cause, but *will* cause.
10k on a filter is 10k, doesn't matter if it's 5k and 5k or a 10k strait run.