Every year I think it's okay to spend a little more on this costume because younger sister or brother can wear it another year. Aaaaaaaand then that never happens. ;)

I was able to reuse my older kid's costumes when my youngest was still a baby and into the toddler years. I have a girl and a boy so a lot of the costumes my daughter wore don't interest my son. We think it's important to let them choose how they want to dress up each year (within reason) so my son hasn't wanted to use what his sister has. Luckily, we have a bunch of younger nieces we can hand her costumes down to.

I don't think we've had a time where we've actually reused a costume as they always seem to want to be different things each year, but I think it's a great idea if it works. We've certainly passed along costumes to friends or donated them to charities that supply kids in need with Halloween costumes.

I let my children pick out a new costume every year but we save the older ones for "play clothes".

When my kids were little (2 and under) we definitely reused costumes, including hand-me-downs from my nephews. They were too young to decide what they wanted to be so I would decide for them and obviously choose what I already had. With two boys first, this was pretty easy. Then my third is a girl so it got a little more difficult. When she was almost two she loved dogs so she wore her brothers old doggy costume and I added a pink bow to the dogs ears and she wore pink pants to make it a girl dog like she wanted.

I bought them used when they were young so had no problem getting them each their own costume, that fit their personalities. Plus their sizes didn't match up since my oldest was 11 months on his first Halloween and my youngest was 3 months on his first Halloween.

I let my kids pick what they want to be every year and they always pick something new.