On my first few solo's I had a worrying tendancy to not do my landing checks. This prompted me to rights "CHECKS" on my kneeboard, and never forgot about them since.
As for the HASELLcheck - I totally forgot what some of them were yesterday. Luckily I had the checklist to hand, and went through them. Always good to have it there.
I expect if my instructor were sending me off solo, or we were going futher away, he'd veryify my sums. I think yesterday was a mini "test" to make sure I could actually do it. He checked my final figure for heading, and seemed to think they were ok. I'm in the habit of putting a large arrow on my chart now too, makes it a lot easier for quick checks etc.
My next navigation is a longer route, so will likely go through the calculations. Then I do them both solo (assuming everything's ok in the dual), and then start the land-aways!
And you're solo - don't think 18 hours is "quite a while" - I'd say that's pretty darn good! But like you said, doesn't make much difference in the end!