Hi Michael –
Yes you can release ladybugs over several days. The following release instructions will help.
Ladybugs will arrive in a cloth bag ready for release. If it is not convenient to make an immediate release, you should place them, box and all, in the refrigerator. Make sure to include an apple wedge or damp piece of sponge/ paper towel in the box to increase the humidity level around the bugs. (Most refrigerators are frost-free and will dehydrate your beneficial insects.) Remember: The longer they are refrigerated the higher the mortality will be. DO NOT FREEZE.
To release ladybugs, simply water your garden and shake them out close to pest populations. DO NOT release them during the warm part of the day when the sun is shining. With sufficient food available, the ladybugs will likely stay in the area. However, it is not uncommon for them to take flight if not enough food is present. You may want to supplement with other food sources such as commercially available insect food — our Ladybug & Lacewing Food, for example.
Note: Ants in the area should be controlled, since they protect honeydew producing insects like aphids.
Hope this helps!