Tubes wear out in a few thousand hours of use, and elco caps in a few milion hours mostly when they see a lot of current go trough, but for the rest, if the electronic devices are wel ventilated it should not damage the gear. Your ears may get damaged if the volume is to high (but i suppose it's not), but for the rest don't worry to much. Even with tubes, they can mostly be replaced easely when they wear out. And elco caps wear out over decades, so if your amp or speaker is decades out you may have to replace them.
I got a pair of Kef Chorale speakers from 1971 from a friend to repair, and it's just dried out caps from the crossover that needs to be replaced. The B200 woofer and T27 tweeter are still in very good shape and the cabinet is only cometicly lightly damaged.
But those speakers are 53 years old and were in daily use. Amps won't last that long without revision and recap, but also decades normally. And they can be revisioned that they will last another few if they are older (non chip) designs and the parts (or replacement parts) are availeble. I still got a 1982 Luxman C-02 preamp in storage that works perfectly with only one recap in 2016. I don't use it at the moment (i have many parts of hifi system arround), but if I need it, it will still work as intended.
Modern quality gear should not have a problem with being used for hours, it will wear out a bit faster, but not in a way that it won't last it's normal lifespan or beyond.
