Fios Upload Speed Flux

My upload speed-test is consistently 150-200 mbps sometimes after i restart the modem and sometimes 300 mbps (max i pay for). the only difference seems to be luck when i restart?

I can go weeks at 300 but restart and get stuck slower.. but if i keep restarting till i draw the higher speed? this legit or am i crazy?

someone smart tell me whats really happening, is there some "node" or somethings i sometimes connect to thats slower then normal?