Advice on Maintenance and one issue

Hi guys, I have a 2000 Tacoma 4x4 4Cyl 3RZ-FE. Currently just hit 242K with no problems whatsoever. I'm figuring it's near the time to replace some parts before they actually leave me stranded. So far, I've only replaced the battery once, front/rear shocks, front driver wheel bearing, O2 sensor (before the cat), radiator flush/thermostat, and regular brake pads etc. I change my oil every 5000K with 5W-30, have done transmission fluid at the normal intervals, only have changed my rear diff fluid once and I have once gotten all the zerks filled up at jiffy lube. Anyways, that's the vehicle history.

I plan on replacing the starter and alternator soon, since I take this out to mountains and desert quite often, I'd like to have these key but basic parts in tip-top shape. I recently had a problem in the mountains where the truck wouldn't start. I turned the key and it sounded like it was turning over but it just didn't completely start up. After a couple tries it finally started up. Any ideas? The plugs have been changed recently as well as the fuel filter. Battery tests and alternator are good too. I've read that it may possibly be the fuel pump? I can imagine it going bad after so many miles but I haven't noticed anything while accelerating uphill. I haven't ran into this issue when the engine is hot though. I plan on driving this thing till it won't go no more, so any suggestions on preventative maintenance is welcomed. Thanks.