Experts advise fertilizing 3 times a year here, Sherry. Spring, summer and fall.
Mind you, the climate here is very different, and we do get lots of heavy rain in the summer to leach away nutrients. Combined with a lot of places having nothing but sand for soil, drainage is not an issue but nutrients do need to be added/replenished regularly. I'd think a pot with good drainage would be a similar situation.
Sadly, nobody's planting citrus here these days. Everybody's got The Plague. (Citrus Greening disease - Huanglongbing) including my lovely little Meiwa kumquat, which as you say was very handy for snacking upon.
