hi!
well, when I was poor I repaired all sort of stuff, including tv's.I still do it for friends, some neighbour had his tv set died in quarantine time.
so, lot of people told me their set died after it was switched off for holidays or something alike.
found dried electrolytic capacitors, replaced them, all ok
so yes, your friend is not wrong.in fact, datasheet from major factories specify that, even after keeping them in temperature/humidity controlled storage area, the electrolytic capacitors needs to be polarised to recreate the oxide layer.
you see the resemblance, other 'genies' here don't.so I can confirm from practice that electrolytics live longer (or they don't blow the pwm controller away) if you keep them UNDER VOLTAGE.any philosophy around the subject is non-professional.
they are just like our muscles, if you don't use them they get weak sort of speaking.that's what panasonic and others are saying, I just repeat.
best regards,pierre