Is it advisable to have an all tube system?

Besides tube replacement cost, can the sound be taken too far in any one direction?
Depends on the equipment. Cheap tube equipment will Good tube stuff will sound natural. System synergy, of course, has a lot to do with it. Use tube gear that does not use a lot of tubes and that helps with maintenance cost. For example, avoid preamps that have a bunch of tubes; why would any more than 4 tubes (2 would be better perhaps) for a phono stage and 4 for the linestage? One triode tube can be used for a linestage and a pair for a phono stage. Some phono stages (think Hagerman Trumpet) have as many as TEN tubes just for the phono stage. Same thing with amps; get amps that use easily obtainable tubes and shy away from rare NOS tubes (WE 274B, Mullard GZ34, Telefunken 6922, that sort of thing). Stick with modestly priced tubes with good life such as 300b, 2a3, el84. More powerful tubes such as the 211 and 845 can cost a grand for a pair of true quality NOS.
Well, I suppose that if you are using tubes to provide a tonal cure to a problem with other components or set up and keep buying stuff that errs substantially on the warm side of the spectrum, it could be a problem.

But, if you are trying to get that mid-range/high end naturalness (call it airy, bloom, whatever) without emphasis on a certain tonal balance I don't think you can over do it. The great thing about tubes, though, if you wish to change the tonal balance a tad, all you need to do is change tubes. A few bucks. With SS if you wish to alter the tone, such as excessive brightness, or some such illness, you either have to buy new components (with tubes :-)), or signal bending cables and IC's.

Obviously thats just the opinion of a person who has found tubes optimum for his ears and can overlook their short comings. I keep two SS amps on the premises just to remind me on those days when I feel anxious.

But, FWIW, you don't need a tube tuner, I'm not so sure about a CDP/DAC, and I wouldn't be without a tube phono stage and preamp. Amps and speakers should be matched and tubes aren't really an absolute necessity with many speakers, in fact they may not be optimum at all with quite a few speakers.
the days of tubes sounding 'tubey' are long over.

My integrated amp that I bought for $1300 is so neutral that most would not be able to tell if it was tube or solid state based on tonal balance
I find that Audio research Preamps are a little leaner than CJ's but still provide great detail soundstage etc. CJ Tube amps are lush. I combined and ARC SP16 with CJ Premier 12's and for me this is a perfect match, with my Aerial LR5's which were a little forward.Depending on your listening habits and equiptment Preamp tubes can last 3-5 years and Power amp tubes up to 2-3 years or so
Anything can be over done, to cool down some of the warmth in tubes I use nordost speaker cables. With a CJ Premier 16 preamp and Premier 11a amp I hear no bloom at all just pure music. Though I did hear some when I audioned a new B&W 803D. No other speaker gave even a hint but their resolution is just amazing. Hope this helps Michal