Only if you
insist on keeping [peanut butter] at room temperature.
 I keep mine in the fridge, and never need to stir it. 
 Doesn't it get too thick
to spread that way? 
 
Only if you (a) want a thin layer and (b) are trying to spread it on a
substrate with little to no mechanical strength.  Oh, and (c) don't let
it warm up a little first, of course. :-)
Neither (a) nor (b) are generally true of me.  When I eat peanut
butter, it is usually in the form of a mix of about equal proportions
butter, peanut butter, and jam, which is then eaten with bread (real
bread, bread with substance and taste to it, not "bread" you can wad a
whole slice of up into about half a cubic centimetre) in about 1:1
proportions.
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