Hi Jacek,
I work as a Research Computing Facilitator in the Center for High Throughput Computing, on campus, which produces the HTCondor software.
You may get a more specific answer from the administrator of the WEI's HTCondor pool, who will have configured the specific policies for it. In the CHTC pool, for example, we configure our execute servers (where jobs run) to allow jobs to be pre-empted by higher-priority jobs after 72 hours. This effectively establishes a 'cap' on how long jobs are guaranteed to run (barring power/network interruptions, etc.). Such runtime caps are implemented usually to balance factors around slot turnover, fairness, and a desire to not run jobs that are too long (because longer jobs are more susceptible to other types of failures, and because computational work can generally be run more efficiently by splitting a long job into multiple shorter jobs).
There are other potential reasons for eviction, depending on the specific configuration settings, such as interrupting jobs that use far more memory or CPUs than the amount requested. At some point, HTCondor will automatically evict in such cases, purely to keep the execute server from crashing.
If you're not sure who the administrator of the cluster is, let us know, and we can help make a connection since we're on campus. Please otherwise let us know if we haven't helped you get to an answer, or if anything I've described isn't very clear.
Best,
Lauren Michael