I have a hood seafurl 810 (original). It is worn in many ways. I've replaced the upper swivel, and done some things to keep it going, but the joints in the furler tubes are all loose and cause staining on the sail and make it hard to adjust halyard tension. But, the furling bearings all work well.
But, as others have noted, these things don't affect sailing performance. If your bearings are worn out and have lots of resistance, or other things are no longer working correctly, you can still order parts for these and possibly bring it back to life and failing that, buy a new one. I have probably spent $600 on bearing and parts on mine in the 13 years I've owned it. It should now continue for a good number more years. A new furler would be a couple of grand.
When my mast is down for the winter I plan to take the forestay off (with furler tube) and either put some epoxy or some 4200 into the furler tube rivet pockets (if you have a Hood furler, you will know what I mean) on the tubes while keeping the sail slot aligned. This might alleviate my issue with the work joints.
I have heard that changing the "Line Drive" drum to the normal single line drum (from Hood) might not work with the below deck configuration. I've thought about this change, but didn't want to move everything above deck as might be required. I don't like the single continuous line furling design as it's very hard to "reef" sail reliably with this (line can slip out while sailing).
Harken sells a compact furler that is designed to be below deck. I don't know if it could be made to fit, but that might be a consideration.
Cheers