I am making my in-laws 50th Anniv. cake this saturday. Can I frost and pipe swiss-meringue buttercream on cake 24hrs ahead of time and still have it be delicious? Will the buttercream hold up in the fridge that long and then be able to sit out for approx. 7 hrs successfully? Anyone with make-ahead experience.........I would love any advice you have to offer!!

i dont know about the sm but i always do my bc wedding cakes ahead of time, a doy or two, and have not had any problems with freshness. I usually dont put them in the fridge unless the filling needs it (like fruit).

I don't know about smbc either. I've been known to leave my BC out for 2 days before delivering. It's not a recipe that needs to be refrigerated. I'll give you a bump, maybe somebody else will know.

I'll give you a bump too, it would be interesting to find out.

That's how we do ALL our wedding cakes at the bakery I work at (busy local bakery; ~150 wedding cakes/year). The SMBC comes to room temp while on display at the wedding reception.
We refrigerate all completed cakes. Mostly because our fillings are whipped cream based, but also because the SMBC gets nice and stiff in the fridge, and is more 'stable' that way. Makes deliveries MUCH MUCH easier!!!
However, SMBC IS stable at room temp for several days if you don't want to refrigerate for some reason.