Perhaps somewhat of a system could be implemented, whereas certain requirements should be covered in order to obtain it (I am paraphrasing the said above). However, what also could be taken into consideration is the following: the more days that you log in (for an example 7 day streak), the bigger the bonus will be - and after those 7 days, it resets and you need to build it up again. I do believe that way, players would be encouraged to hop on more often.