FeynCalcToLaTeX[exp] generates LaTeX with line-breaking for exp.
FeynCalcToLaTeX[expr, 500] generates LaTeX for exp where 500 is the Window width setting for the Mathematica frontend. Increasing its value will generate less line breaks.
NB: This function appears to be broken in the recent Mathematica versions, most likely it will be rewritten from scratch in a future version of FeynCalc.