Is it "safe" to keep external hard drives awake 24/7 ?

One small niggle I have is the 6 external HDDs I have, which are connected to docks, constantly take about 5 seconds to come to life when needed, I suddenly hear them whir up when I click on them or save to them. I have turned off "sleep" in Power settings, but this doesn't seem to help. I saw some software that can keep drives alive by writing a small text file to them every few minutes. Can someone tell me if there are any negatives to keeping them awake 24/7 ? My PC is left on all the time. Will they overheat, or is that only when they are having a lot of use ? Is it no different to my internal drives being on "0" in the power settings ?

Thanks !

It should be no problem leaving them run all the time. The only time a hard drive generates heat is when randomly seeking for long periods of time. However I personally have have about 8 external drives all in enclosures. I always like to have a fan. I do not leave them run 24/7, since they are primarily used for backups. But when they are in use, I'm pumping large amounts of data in the shortest period of time and they do get warm in that environment.

It's no different than internal drives, assuming the external cages have some kind of cooling system. If not, those drives will likely run hotter.

On a side noe, if I had 6 external drives running all the time, I'd ditch them in favor of a NAS. My NAS runs 24x7 and uses 4 drives that I chose, knowing they were designed to be run 24x7 (WD Red). I get the benefit of a RAID array, instead of running multiple single drives, as in, one drive dies, I lose nothing.