It seems to be pretty much universally agreed among Christians that we ought to tithe 10% of our income. (I was attempting to find a biblical reference for why this is, and it turns out to be complicated). But our income represents the fruits of only a small portion of our lives - in developed countries, most people work between 1500 and 2000 hours per annum, or an average of about 3-4.5 hours each day. If we allow for eight hours being spent sleeping, and working for two-thirds of one's life (which is a pretty large overestimate - many people spend barely half their lives in paid employment) then this represents a tithe on about one-sixth of our waking lives.
I propose that we ought to be tithing from the rest of our time too. If we have twelve hours a day (on average) when we are not in work or sleeping, then this suggests a tithe of eight or nine hours per week. Allow three-and-a-half hours for church and a midweek bible study/fellowship group, and we ought to to be spending roughly forty-five minutes to an hour each day praying, reading the bible, and directly worshipping God in other ways.
Of course this shouldn't be taken as "45 minutes, that's my duty done!" - God loves a cheerful giver - and it doesn't mean that we can't do all things in our lives to the glory of God. But it doesn't seem like a difficult target - 20 minutes of praying, which can be spread throughout the day into two or more sessions; 10-15 minutes each of reading the bible and reflecting upon it.