As above tubes will burn out if left on. There are similar threads in the archives. Also please avail yourself to Audio Asylum Tube Asylum. A very knowledgable group of enthusiasts have addressed this issue.
That said I had a Jolida CD player with tube output. I rolled the Jolida tubes (Shuguang?) to NOS Mil Spec Mullards. The change was immense and worth the cost of the tubes. When the CD player gave up the ghost I retrieved the Mullards and tested them after a number of years in service. I didn't leave it on but played it often. I tested the tubes and much to surprise they very strong. So for whatever reason I have seen equipment that was not hard on the tubes. Could it be the design? Possibly I really don't know.
I hope this doesn't confuse you. All my other (a lot) tube gear I turned off or used up tubes listening.
That said I had a Jolida CD player with tube output. I rolled the Jolida tubes (Shuguang?) to NOS Mil Spec Mullards. The change was immense and worth the cost of the tubes. When the CD player gave up the ghost I retrieved the Mullards and tested them after a number of years in service. I didn't leave it on but played it often. I tested the tubes and much to surprise they very strong. So for whatever reason I have seen equipment that was not hard on the tubes. Could it be the design? Possibly I really don't know.
I hope this doesn't confuse you. All my other (a lot) tube gear I turned off or used up tubes listening.