Mfaktc keeps going after a factor is found

[rcv]

Originally Posted by Karl M Johnson

So there's no real point in continuing a TF job after a factor was found ?

People also run ECM on numbers that already have two LL tests. Is there any point in that? If the only goal is proving or disproving Mersenne-primes, then no. But, there are other goals and other considerations. For example:
1. mfaktc (and I presume mfakto) do not search for primes in ascending order.
1a. I believe the "credit" awarded when a factor is found is assumes you have worked the numbers in ascending order, so unless you finish the bit-length, you will get more or less credit than you deserve.
1b. As axn indicates, you will not necessarily have found the smallest prime factor. I believe some research depends on knowing the smallest factor of a composite, but don't ask me for references.
2. As mentioned above, some people are attempting to fully factor the (smaller) Mersenne numbers. Completing the bit-range you have partially factored may aid such efforts in the future.
2a. I believe the gimps database only keep track to the bit-level of how far a number has been factored. For example, if you only do part of the 69- to 70-bit range, it knows there is a 70-bit factor, but it only remembers trial factoring has been completed to 69 bits. [Recent information makes me wonder if gimps actually retains this information after a factor has been found, but I'll need somebody else to answer that.]
3. Knowing how many factors of a given size exist may be helpful to researchers attempting to validate unproven hypotheses concerning distribution of factors in Mersenne numbers. [Related to 1b.]