Mine are usually really regular now but it's taken 3/4 years to get that way. :/ And even the other day I came on for like, a couple of hours then came back off again which was strange.
Mine are really shit though, they're not really heavy but they last about 8 or 9 days and I'm like WHAT? So yeah, I'm a cunt for over a week to everybody in sight and every couple of months I get a really bad one where I just crawl up in a ball on the floor with a hot water bottle and want to die.