We bought a static last year after being fairly seasoned campers (will be flogged!)
Bought it last June - it was about 18mths old but the previous owner only used it for 10 nights so got a better deal than on a new one.
We spent all the summer hols there, most weekends, October hols. We LOVE it - it's 3 mins walk to the beach, so don't have to rely on the car once we're there.
Everything is there - food, beach stuff, bedding, toys etc etc - so don't need to spend time packing. We've bought 2nd hand canoes we leave there, the kids have old bikes there. There are other children to make friends with. When they're older they'll be able to join the sailing club to have lessons.
It sleeps 8 incl the sofa bed, so we had friends to stay a lot - great when DH wasn't there, and DD loved having her mates to play with, and I loved having friends to sit outside & drink wine with in the evening.
We spend much more time outside (need good waterproofs, but kids don't care about the rain if they're dressed appropriately - we even built sandcastles & dams in the rain)
We also spend more family time together - no excuses for DH to potter in garden/sit & watch rugby etc
Kids are now 5 and 3 next month - they love it!
It's definitely not a financial investment - they're expensive, the rent isn't cheap - but we're rubbish at planning ahead to book holidays in the school holidays - I reckon on up to £1000 per week to book a cottage in school hols, so that puts it into perspective a bit more.
Ours is 2 hours from home door to door - any further than that and I think it would be a bit far for weekends.
We were both quite wary about buying one - I thought I'd get bored going to the same place (I used to go backpacking all over the world!) but I realise that kids on the beach = happy kids = happy parents = happy hols
Which area are you thinking about?