There is or was a fella called the 'Fireman' who would probably put a strong case to you NOT to chase the odds on conveyances

From memory he only backed odds on 2 yolds racing in Brisbane, did very well for a while then came a big cropper

All I would say on the subject is why bet so short? Look at the results on any given day & tally how many winners are odds on. That should be enough of an incentive to go longer.

To add a post script - theres not much sweeter than collecting on that 30/1 shot, whilst getting back $145 for my $100 outlay just doesnt do it for me