Rectifier Tubes: Do they need to be changed/how often?

People always mention changing pre and poweramp tubes and their tube life/effect on tone. How long do rectifier tubes last for usually? How do you known when you have to change them? Also since it's never brought up in tone discussion, i'm going to guess that brand name/type don't have that much of an overall effect on tone?

Some people think the stock 5U4's are a little mushy and/or saggy and prefer a GZ34 instead.

I like the sound of the stock rectifier myself and I don't find it to be mushy at all personally.

tubes make a rediculous difference on your tone.

usually preamp tubes last at least 2 years
power amp tubes are good for a year, maaybe 2

but it all depends on how hard you play your amp. how loud, how often.

my band practices 3 times a week, at loud volumes, for 2-3 hours at a time. it eventauly takes a toll on the pwer amp tubes. i have to replace mine yearly

to give you an idea of how long they last, the rectifier in my 73 deluxe reverb is original, still going pretty strong. with heavy high gain use, all tubes will degrade after a year or two, but if the amp is used sparingly/not at all/low volume, tubes can last decades. as to how you can tell when they are failing...I believe they simply fail, although I've never experienced this myself. Perhaps it's failing in the fender and I don't even know it!

In terms of tone from manufacturer to manufacturer, I think it's pretty limited, like...not at all unless there were problems with quality. ALthough people do shell out big bucks for NOS rectifiers so there must be something there. The biggest difference would be found in the type as outlined in the above post, as long as it's safe in your amp. I think you would be pretty safe with any of the major brands: JJ, Mesa, Groove Tubes, Svet, etc... Probably just change them every other power tube change to be safe, although thats not really necesary. Not an expensive tube so why not?

edit: every other power tube change might be a little excesive...i think a call to mesa is in order.