I use an older oms square style analyzer with a din flow restrictor for dive boats and nitrox, it is small and easily carried in a dry box. For trimix I use an analox Ata pro (which could be used for oxygen or helium)
Browse ebay and you will usually find some for cheap, like 50 to 60 bucks cheap. Then just throw in a new sensor and bingo, you have an analyzer. I prefer using a first stage restrictor to maintain an adequate flow of air to test. That way I have consistency in my results.
You can never test enough. Test it after the fill, before you leave your house, and before you dive it. And sticker the tanks with your mod. I use yellow painters tape with a green marker for nitrox tanks. Blue tape and silver marker for air. And orange tape with black for trimix. That way at a glance I know what I'm grabbing. Then I retest before putting my mouth on it.
*edit, autocorrect didn't work*