Don't spend 45 mins on a race - that's 6 hrs for 8 races - not viable.

No more than 20 mins per race - you you cannot make a decision after 20 mins - the race is too hard, so forget it.

You need to follow the races for a few months, after that you'll know what to look for. In most races there are only half a dozen realistic winning chances. Sometimes there may be 1 or 2, other times 10 or so - avoid those races unless you get very good odds about something you like.

Refer to Brumby's stats - you could build a system around those figures that will provide plenty of winners over time.