It’s best to whip your cream right before you serve dessert. If you’d like whipped cream that will stand up" longer, so you can whip it ahead of time, here’s a nifty trick: Instead of Splenda and vanilla, add 1 tablespoon of vanilla sugar-free instant pudding mix powder to your cream before you whip it. Glorious.
Now turn down the mixer speed, and taste. Does it need a little more Splenda and vanilla? If it’s not quite sweet or vanilla enough for you, add another tablespoon of Splenda and another 1/2 teaspoon of vanilla (and next time, just add the whole quantity before you start whipping) Keep whipping on the lower speed until the cream is quite thick, then turn off your mixer. (If you whip too long, you’ll churn your cream into sweet vanilla butter.)