10 minute vs 10 mile markers

I am curious as to what people prefer when planning nav's. I use 10 minute markers on my charts for a number of reasons.

I figure out what my groundspeed should be before I take off using the weather. Then I know that in 10 minutes I should be nearing a mountain, town, lake, whatever. Even when the weather forecast isn't that accurate I have found it to be quite easy to adjust in flight by a minute or two. I also like the fact that 10 minutes is when I am doing my CLEAROF checks so it aligns nicely with this too.

But how do I know when I have gone 10 miles? By my watch I guess. I work out groundspeed and then look for the landmark at 5 mins, 6 mins or whatever the interval works out to be. Advantage here is that 10 miles is 10 miles, no need to change anything in flight. But, 10 miles won't line up with the CLEAROF checks.

You could find many pro's and con's with each but I am curious. What do you use and why?