Hi guebeli1, welcome to the forum!

WCG scientists and techs decide how long to allow for return of work units (WUs) for each of the science projects that WCG supports. At the moment the shortest are just 24 hours, and the longest 10 days. The actual amount of CPU time required to process each WU also varies from project to project, and over time the WUs for each project can vary in length. Some projects are more deterministic than others and all WUs are about the same length, while others have quite a wide variation. And, of course, more powerful computers will process them quicker than older and slower ones. You will need to run a few to get the feeling for how your machine copes with them.

Loosely speaking, if your machine goes beyond the time limit, another copy of the WU will be sent to another volunteer. If they return the WU before you do, your copy will be marked "Too late". If this is happening a lot for you, then either you need to look at a different science project, or you need to do something to complete WUs more quickly (if that's possible). If you are running more than one BOINC project, and you want to support WCG, then perhaps you should give WCG a larger resource share? Take a look at the projects tab in the advanced view of the BOINC manager.