Depends what keywords you're targeting and what competition you're up against. Though there is no such thing as too much backlinking so keep going with it. If you're using some automated software then you can do thousands of links a day but if you're doing it manually I guess 30 or so is realistic.
It is not time to increase more no of links. It is time to perform smart work. So I suggest you to increase back links which are from same category website theme and it will help you more if you are getting these back links from Do Follow links attribute.
I am Not Used It for Daily Bases , When i have time I used to Build it for website .
Always Go with Number Of techniques in order to place link to cover the criteria of natural linking .
However their is no boundation how many links , yes boundation are with how Quality Links .