Badluk

If I play Tekkit Classic for a very long time (which I can only guess is over a couple of hours, but I can't tell how long for sure) it starts to have these occasional lag spikes that progressively happen sooner and sooner, until it makes the game nearly unplayable. (which only happened once, when I had forgotten to close it overnight) An annoying issue that also results from this is that the launcher doesn't come back up afterwards. I've only found a fix for the launcher crashing, where I leave the launcher to "Stay Open." It usually doesn't crash now, but the lag spikes are still there and (as far as I can tell) are unpredictable. I'm using 4GB of memory (and could use more) so I'm fairly certain that it's not the issue. I've had the same problem before I increased the available memory, and it happened the same way over roughly the same period of time. Is there anything I can do to solve this, or is it something with Tekkit Classic that everyone is getting? Thanks in advance for any help!