sss Old guy here is thinking about replacing tubes in two different zen amps but want to be safe...need some basic help.  I only replace tubes when they go out or have Decware do an update/check every few years.  I don't have a tube checker and it is time consuming and expensive to have my local audio guy do it for me...he also isn't aware of all the tube choices with these amps so I need decware forum advice. Should I just replace power tubes or simply replace them all at the same time...?  I have old nos tubes bought from guys at decfest and can simply replace them but then I thought I should replace them in 3 steps and check the amp at each replacement to be sure that everything is ok...in other words start with each rectifier, test & play, then power tubes, test & play, then signal tubes.... then throw out old tubes that I replaced.....I also have 2 decware preamps and thought I would do the same process and after the power amps zens are done start on the preamps so I can be sure that every tube is ok and working fine in the replaced power tubes in the zen before replacing the preamp tubes.    I have a stash of all tubes including choices in rectifiers and power tubes but wondered about trying the 6n2p-eb tube in the zen...is this ok and does it work...is it recommended...I also have a new (to me) rachael and also thought about trying this tube.  I also ordered some croy'd tubes which arrive today and hoped to get more life and better sound....worth the cost?  I see that some people here replace power tubes yearly or every six months...but shouldn't rectifiers last 2 years or more??  with 3 decware amps I'm just looking at an easy plan to update/replace tubes....I also don't want a rectifier to blow and take out my amp....it has never happened to me but?????....also since I spread usage in 3 amps, i.e. one in small bedroom, another in living room, another downstairs I think that total usage is significantly less..do you need to estimate hours/time on amps????  Also have one decware phono zp3 and have less than 2 years on it and the aforementioned rachael so I haven't got it into the mix yet of tube rotation...what to look out for....too many amps ...too many tubes to worry about...and not enough time...I just turned 70 some tubes will outlive me..!...any helpful ideas will be appreciated as I march to senility....
dla405j

Just a few points. . . .

I use my amps a LOT and I change my output tubes about once a year, that seems to be the average.

I don't change rectifiers that I like unless they have a problem; I've used some for years and if I like them I want them to last forever and they usually fail before they start to deteriorate sound wise. A good rectifier should last years.

Preamp tubes likewise last quite some time. .. I generally get three or four years out of them when I leave them in that long.

Personally I like the cryo'd tubes and believe they are worth it, in part because my favorite supplier (Ron Sheldon of cryoset.com) tends to cryo tubes that have been screened for good qualities. . . . I really have enjoyed using cryo'd power, preamp and rectifier tubes.

Anyone have difficulty with the OA3 regulator tubes? One blew out on me second time using my amp. Any ideas welcome.

I put in an order for a pair and noted the situation on the form so we will see monday how it works out. I reached out to steve as well so i should know what is up once a new set gets to me.