If anything it will get less stiff feeling. If youre a dynamic player who hears nuances and is about "feel" youll notice it more than someone who throws OD on everything and likes smeared tones.
But it wont lose definition until you get too hot... going past 45 the tubes break up more. Definition starts to fade. Everything gets softer with fuzzy edges the more you go.
The sweet spot for me always been 36-39 even though I did really love my TAD blackplates at 42 in my SLX 100.
The only amp Ive liked "purposely colder" was a mkiii Herbert with every power tube I tried in it.