Like us down in the tropical West of Cornwall.You're almost as cynical as me. 'Normal' Clik is just the same. Clik Extra just has more ai so it lasts a few weeks longer. Useful if you live in those tropical areas where the grass grows all year round and the fly season is longer.
Personally I think Ectofly, crovect and Molecto are a waste of time for prevention. Effectively you need to have a blue sheep/lamb for 100% cover. just use crovect as a treatment should we get flystrike before shearing which we did this year.