It's not too much if you can pace yourself and are prepared to slog, just know don't expect punchy, point-after-point of doctrine, like you are reading a book of modern apologetics, since it is thanks to these men that apologietics, being a distillation of the doctrines they received, upheld and passed on, exists in the first place. This means that you will be reading entire books on the trinity, for example, rather than summarily informative chapters.
Bear in mind that what you reading is the Church in its formative years when men, guided by the Holy spirit, were trying to work out the intricacies of the Faith and to combat errors and heresies,so you will need to be canny and not take absolutely everything as utterly true and definite (e.g. with Origen).
Try here if you like:
http://www.newadvent.org/fathers/index.html
It has most of the Fathers in alphabetical order, the canons of the first seven Ecumenical councils and some apocryphal or non-canonical stuff at the bottom.