Wyeast smack pack

I smacked a wyeast pack to use same day (sunday) but i didnt get around to using it that day or monday evening and now i might not have time to brew this evening. Does anyone know how long the yeast will be good for after i have activated it?

The yeast should be fine for some time. Your best bet either way is to make a starter for every batch. This will increase your yeast cell count to better pitching rates, improve both lag time and fermentation time, and finished quality of the beer. Mrmalty.com will have pitching rates based on style and OG if you don't brewing software like beersmith. Starters are easy to make and improve the quality of your brew.

If you smack one it is fine for a couple of days at room temperature and maybe a month if refrigerated.

All liquid yeast packages have less yeast cells in them than is optimum for average beers. Starters are not necessary, but highly recommended.

Mrmalty.com
YeastCalc Yeast Calculator

Thanks guys!