First question - what kind of goats are they and are they pets or breeding/producing animals? Male, neutered, or female?
In broad terms adult sheep should be boostered with Heptavac P once per year after their initial two-injections-four-weeks-apart course as lambs. Goats however have been shown to not build up great immunity to clostridial vaccines in general, and to multi vaccines in particular. So as goats mainly are susceptible to tetanus and enterotoxaemia (more so when younger), the vaccine with the lowest number of individual vaccines in one bottle is Lambivac. Initial course as per sheep, then minimum 6 monthly booster, some of us doing it four monthly for the first couple of years, then every six months. Sheep farmers use Lambivac for lambs that are sold for meat rather than breeding.
That leaves the pasteurella protection out for goats - therefore use of Ovipast is advised IF you have a problem with pasteurella on your farm. Again, same initial double course, then 6 monthly boosters from then on.
However many goat breeders do use Heptavac, as it is the cheaper option, especially if your herd is quite small. The reason I asked if they are pets, there is a theory that as they get older they become less susceptible to clostridial diseases, especially if they live a rather stressfree life. I would have a word with your local vet and get his opinion.