My replacement glass fiber reinforced PTFE liners for the Ultimaker II hotend arrived.
While replacing parts I looked up just how long this Ultimaker II has been printing so far:
machine has been on for 2954 hours
printing for 1855 hours using 1166 meters of 2.85mm filament.
The PTFE is pretty banged up for sure.
In the forum people talk about 300-500 hours before seeing serious degradation.
I replaced the PTFE,
doing a cold-pull cleaning in the process,
Added a piece of aluminium foil,
cleaned the extruder gears
cleaned the bed
...now let's start with the next 2000 hours of printing.
I just found out you can get them (for a premium price) at Reichelt or
remakes (no mention of glass fiber) at another German Store and in China too.