Ante Post Racing?

MP33

I,m not really clued up on racing but was wondering if i could get any help or tips for Ante-post racing

I,ve been keeping an eye on the 2000 guinees nxt year where Power was favourite, at 7/1 a few weeks ago until Harbour watch won a race the other day and went in from around 25/1 - 12/1 and now 10/1

Power was beaten by Lilllborne Lad who was 28/1 for the 2000 guinees EDIT just spotted it at 40/1 at another bookies so had another£3

I had a £20 on Harbour watch before that race for the guinees as my thinking was if he won it at a very short price he would go in for the guinees and even if he lost it night have been an off day and he,s still got a chance for the guinees

Similary , although i waited until after the race this time I just had £5 on Lilborne lad at 28/1 as it had just beaten the so-called fav only a week or so ago 

what i,m trying to find out - Is it best to back ante-post for the big races in the long run if your quick off the mark in getting your bets on even though you have to wait several months for a possible payout and also considering as i mainly do it on the exchanges you don,t get your money back if the horese pulls out before? (and is this common) ?

Hope that makes sense