Drinking as much fennel tea you want everyday is perfectly safe.
Although some people start with drinking only one or two cups of fennel tea per day and then up their intake of the fennel tea after a month or two of drinking the fennel tea.
But there's no harm in drinking more than a couple cups of fennel tea everyday if you want too.
I drink around two cups of fennel tea everyday which is enough for me but you can drink as much fennel tea as you want too without any problems.
Drinking fennel tea helps with digestion and treats bloating, gas, cramps, and can also act as a diuretic.