You may wish to prepare them the day before you plan to serve them. Aspartame stays sweeter longer during heating if the other ingredients in the recipe are acidic like fruit. It will also stay sweet longer if it is mixed with another sweetener. Any artificial sweetener is sweeter when combined with another sweetener. Sugar-free puddings and gelatins usually substitute perfectly in refrigerated desserts and congealed salads.
Spices can mask the aftertaste of some artificial sweeteners.
Using less of an artificial sweetener then needed to exactly substitute for the original amount of sugar in the recipe may also make the aftertaste less noticeable. Cinnamon and vanilla make a food taste more sweet with less sweetener. Sugar makes a food stay fresh longer because it helps retain moisture. You will need to cover any sugar-free baked goods well and refrigerate or freeze them to maintain freshness.