I would prefer the lab slowly accumulate science over time. Of course, it would need to be continuously crewed and in an interesting location such in orbit around a planet/moon. Put a cap on the allowable science accumulation depending on the planet/moon it was orbiting. A lab orbiting Duna would have a much higher cap than one orbiting Minmus, etc. This would avoid the issue of science spamming and provide a reason to have multi-Kerbal missions to other planets. Combining with life support mods would add an interesting game dynamic, where you would be concerned about the longevity of missions, rather simply how many science instruments you can stick on the ship.