I used to have a 557. I always left the power on except for when away e.g. holiday. Great amp, never short of power on both Magnepan and Xanadu AW10 Reference.

Living room: Ansuz Mainz8 C2, Uptone Ethernet Regen, Grimm MU1, Audionote (UK) DAC 5 Special, TT2, M2RIAA, Audionote (UK) OTO Line SE Signature, Fleetwood Deville SQ
sold (Q1-2024): 818v3, DSP7200SE
Office: MS200, audio engine A2+
Spare: STAX SRM-323II, SR303, MC200 (Roon ROCK’ed),
Roon: life time subscription