maybe not
remark: your request just doesn't make sense for me. have a look at the following situations:
a) a visit with just one page view for 20 minutes (maybe very interested visitor) and the evar78 set will give you the counts 1 visit, 1 bounce, 0 time spent. what do you get out of the numbers? maybe filter out all bounces for time calculation afterwards
b) a very interested visitor had a visit with page views every 10-15 minutes over 3 hours (maybe drinking some coffee between?). if the visit has the evar touched in one hit at the beginning, the visit shows up in every report with the following numbers: 1 visit, 0 bounces, 3 hours (time for visit!). if you count up those numbers of all reports, you end up with 3 visitors and 9 hours time spent (or maybe 4 visits depending on when the visit started). only average remains the same
i don't know if it is useful to get those numbers in an hourly report other than just for interest. if you really want to calculated on those numbers, better change to a monthly reporting window.