The Dice Bag complains about the number of rolls needed to generate random encounters:
I have always enjoyed the fact that both as a player and a GM I’ve never had to suffer the “oh it’s been 10 minutes of game time I must roll some dice to work out what’s going to happen next” moments. Don’t get me wrong the occasional secret skill check by the DM works great but the structured approach to random encounters that most systems encourage is beyond me.
Taking them out completely isn’t an option for me either. I actually like the supposed randomness the idea can give to gaming sessions if you’ll believe that or not. It’s the ‘regular’ rolling of dice I despise as it turns the game into a series of turns. That’s fine when it comes to combat but for general play it’s to much of a hindrance for me at times.
So how did I every get around this part of the mechanics? For a couple of years I had a small computer program that produced a page full of random numbers from whatever dice you chose to roll. I coupled this with maps that had specific points where an encounter ‘roll’ would take place rather than at set times during the game. It did mean that if a group stayed at one point they shouldn’t come across any enemy until they moved off if they had already encountered something whilst there but these were flaws I was willing to live with.
The obvious solution is don’t roll each turn (or whatever the unit) for a random encounter–roll to see how many turns until the next random encounter. This means that, unlike the system he was using for pre-rolling encounters at certain places, it’s possible that the party will have encounters even when sitting still. For added verisimilitude, they might even have an encounter that shows up during the middle of another encounter if it goes on long enough. While it would be easy enough to devise a formula or spreadsheet that would give you the same frequency and distribution of encounters as most published systems, that’s probably overkill. Just pick a die size that gives you an average time between encounters that seems reasonable, and roll it open-ended (if you roll the highest possible on the die, reroll and add). The open-ended roll means the players can’t use metagame reasoning that since it’s been five turns since an encounter they’re due one on the next turn, but it changes the average roll very little.
This is the reverse of my tip to reduce bookkeeping for things such as supply rules. In general, you can trade off die rolls versus bookkeeping. If you feel you’re rolling too often, substitute bookkeeping by rolling to see when the next “event” is and just track time until then; if tracking too many things is getting you down, abstract it as a periodic die-roll to see if a condition has changed by now. I think “time until” works particularly well for events that would otherwise be rare enough that there’s no point in rolling for them, and when you’re using something you’re probably already tracking (such as time). I think “don’t count, roll” works better for things where you’re only tracking for one purpose, and you don’t actually care what the value is until a lot of steps towards a critical threshold have been passed (e.g. individual ammo).