I agree with Kilarney sailor that a 300 miler is short stuff, so is 700. I have this thing about the Sydney Hobart race which is 635 miles. A 'real' passage is multiple Sydney Hobarts. My longest is 5 S-Hs. Another couple pretty close to it.
Now thats not saying 'been there, done that', what I am saying is that thinking about passages as a time thing, or milage thing is counter productive. Just get out there and don't look back untill theres land on the bow... Hopefully your intended destination.
And do them at a physical intensity that will keep you refreshed, happy, and full 'o beans.
Keep the boat below hull speed. If you see stupidly high boat speeds, like you hear people at the bar say I was surfing at 10 knots, then slow the hell down! Not only does it slow you down but it makes the boat more comfortable, less breakages and you are not so tired.
Get proper sleep and dont fall in the trap of informal watches. Do proper set watches and when you are off watch get the hell off deck and go read a book or, better, sleep.
I did a difficult one last year 1,400 miles up wind by myself. Against the current. Ok it was a tad character building, but i was fine because I was reefed and sleeping. Maybe thats a good line to remember: reefed and sleeping. A perfect cruise
Other thing people keep mentioning is about cooking. Instead of cooking before the trip I always cook proper, great, excellent meals at sea. Learn to do it on your overnighters and then its easy at sea. You need lots of calories because if you normally expent 2,500 per day at home, at sea with the rockin you are probably expending 4,000 or 5,000. No matter how well you eat you will still lose weight. But if you eat normal amounts of food you will get tired easily, seasick and lethargic.
So: Reefed, Sleeping and Stuffed!
I never look at the miles to go unless they are under 1,000 or less on shorter passages. Why the hell do you need to know you have done 136 miles and have 2,675 to go? Just put your dot on the chart and cook up some naughty food
Fix things when they happen. A solo non-stop round the world guy told me that theres no use waiting when something goes wrong. You are solo and day and night make no difference so fix it then and there. Damn stupid advice has made everything go wrong at 2 am!! One night I was fixing the galley pump at 2 am. Dont put the jobs off just do them.
But general maintenance jobs... Forget about them unless they directly relate to the sailing. I.e it would be stupid to pull out the varnish brush! Go have a sleep instead
If you do bugger all on your passage except to reef, sleep and eat then theres plenty of time to enjoy yourselves... And watch dolphins.... And watch waves... And see the stars... And wish upon shooting stars... And read... And....