You can do an exchange anytime that suits you. Just find an exchange partner to do an exchange with.
Possibilities are endless. These are just some examples
Your kids are spending three months in a student’s residence in the UK, why not spend a holiday week or a weekend with them staying with a local family? Can this local family then visit you at home and spend a few days with you?
You go abroad for a long weekend, why not use those few days to stay with an exchange partner? It will be a different experience.
Send your son to a summer camp together with your friendly family’s son.
You are traveling in another country and want to spend an afternoon or go out to dinner with people there … Take advantage and meet a member of the community!
Welcome a foreign kid in your home during the Christmas holiday.
You share a hobby with your exchange partner, both fascinated by photography. Why not take the opportunity to do a photography course together? You will practice the language from your great hobby.
Take advantage of the half/mid-term holiday.