Comment by ruined

it's incredibly algorithm-dependent. if you look into the thesis that originates the 'bootstrapping' technique to transform SHE algorithms into FHE, they determine the noise limit of their specific algorithm in section 7.3 and then investigate expanding the noise limit in 8 and 10.

(written in 2009) http://crypto.stanford.edu/craig/craig-thesis.pdf

some newer FHE don't encounter a noise limit or don't use the bootstrapping technique.