Well, that is actually a good question. When you are new to stropping you can 'roll the edge'. What that means is basically lifting the spine of the razor off the strop so the actual cutting edge of the razor comes in contact with the strop. You should always try and keep the spine of the razor on the strop and not lift it. Also you should flip the razor on its spine and NOT try to go too fast when you are learning. I'd even recommend less laps, i.e. maybe do 15/30 at first and build up from there. 70 laps is a lot, and one can easily loose concentration of one doesn't REALLY try and concentrate. So, imagine you've bought a razor that IS shave ready, or just got one back from being honed professionally, stropping poorly can dull that newly honed (and probably stropped by the honer) edge. Shave with the razor that's shave ready for the first time (and depending on thickness of growth, amount of face you'll shave the first time, etc) even the first FEW times without stropping. I shaved for a few weeks without stropping as I didn't have a strop at first. I actually stropped for the first time on rolled up newspaper. As you get better, you'll strop before each and every shave to remove the micro corrosion, etc etc.

Here's the 'stroptober' thread that had some good videos in it.

Carl