I would definitely bring some sort of snack - a sammich, as mentioned above, or something like fig newtons (a favorite of mine). Electrolytes are also good, especially if you're sweating a lot.
Something to consider is whether you can eat/drink that stuff and continue riding, so next time you go for a 30 mile ride try it out. Gatorade used to make me sick to my stomach, now I like it. YMMV.
You can probably add 10-20 miles to your current max without too much trouble but it might be wise to do some sort of route that doesn't leave you 30 miles AWAY from home if you get stuck.
Oh, and bring two inner tubes on long rides. Don't ask me how I know that.