I think this is ultimately a matter of personal preference, as with a fast, modern computer the difference is unnoticeable. You are correct that each additional step, from a storage space standpoint, is very negligible, and should not be a worrying factor.

To touch on the performance bit a little more...a significant amount of edits can affect the performance of Lightroom. You would need quite a few edits, many dozen at least, before it really exhibits as a problem. Performance degradation will often exhibit when zooming in/out of the work image, when panning quickly, or when trying to make fine adjustments (such as with curves). When processing RAW, the entire history stack must be applied to render the raw image data to the screen.

Additionally, if you keep very large history stacks in place on a lot of photos, I would expect that the filmstrip and the library to exhibit performance degradation as well. Any time lightroom decides to re-render previews (which it seems to do periodically, or if you have chosen to delete them from your hard drive to save space)...the entire history stack for each image will need to be processed.

I think it is generally prudent to keep the history stack to a minimum when possible. I usually follow the same approach...try out a few edits, unroll and reapply the one I prefer to keep. Same thing goes for camera profiles or any other option I can select from a list. In the case of more fine-tuned edits, such as curves...I may tweak with the curves for a while until I like the result...then memorize/write down the current curve settings, delete all my previous fine-tuning, and edit each part of the curve by directly entering the final value. I should not that when tweaking photos that are experimental in the first place, I have built up some fairly large history stacks, with a few dozen edits. I have rarely found noticeable or problematic performance degradation even if I stack up around 50 edits or so, however much more than that and fine-tuning curves or panning while zoomed do tend to develop a bit of a stutter (not much, but enough to be noticeable. It would still take far more edits to actually become a real problem, probably in the area of a couple hundred...which would be kind of insane in and of itself.) (Note: those numbers are on a Core i7 920 @ 3.2Ghz and 12Gb of ram, software on an SSD, catalog and photos on a 7200rpm high density drive.)