I tend to go for 2 litters a year, but it's personal choice really (and because my wee 'husband and wife' team like to be together, the piglets are inevitable
)
Some say it can affect the fertility and number of piglets born, if you breed less ferquently (I guess in mainly applies in high output commercial set-up's) but I've not looked into it too much tbh, sorry
Unless someone can come along and say without doubt that it won't work (AND have the proof
) I'd say try it and see how it goes for you.
HTH
Karen x