Get some blue threadloc while your at it- I lost a wheel & stripped a hex as a result last trip out, silly really as I have 3 tubes of the stuff at home
Max temps ( general guide lines ):
motor 180*F max, ideally 120-160*F
esc 160*F max, ideally 120-140*F
lipos 120-140*F max, ideally... less.
Also as a general rule:
hot motor + cool esc & batts = undergeared
cool motor + hot esc & batts = overgeared
warm everything = just right
hot everything ( or hot esc and motor since massive lipos take alot to heatup ) = way overgeared.
With your 1520 motor & 5s lipo, you should be able to gear for around 35-40mph ( maybe 45mph+ with 6s- depends on temps really ) quite happily I'd have thought- doesnt sound all that fast but these big trucks are a real handful with that much power on tap, they soon cover a field or football pitch sized area and need room to slow down again
