Advice on bias range setting

In the CAD-280SA (V12R with EL34s) manual, Cary states that the bias has a minimum of 220mA and a recommended range of 250-275mA. I have it currently set to 250mA. But before making any changes I was hoping for some advice from the experienced....Why is there a range and not a fixed bias value? Will it sound different at the extremes (220 & 275)? Does this effect tube life? Power consumption? It can't get any hotter can it?
The recommended range is 250-275. Why would you consider anything else? Whenever there is a range I always use the higher setting because it sounds better.
The higher setting will yield a more dynamic sound. VERY slightly harder on tube life. I run my Cary monoblocks in the middle of their recommended range of 150 to 175mA(about 163 mA). I'm using SS below 250Hz, so- I'm not losing anything down there.
I had a Cary V12R and was told by Cary to run it around 240 mA and it always ran fine. You don't need it any hotter. I swear I could cook a hamburger on the one I had.
"The higher setting will yield a more dynamic sound."

A little cleaner, more open and better bass too.
i have cary v12r 240ma is about right,or about 38ma per can run 4tubes or 8 or 12tubes on the v12r.start in the middle toggle switch,one on each side of the toggle switch. 4tubes is about 1/3 power.8tubes 2/3 power 12 tubes full power.this is a good way to try different tubes.