The answer to this is easy, since you provided excellent background - do your plants look dehydrated? If so, I'd say watering every five days or so isn't too much, but it's all dependent on your cultural conditions. Your plants will tell you if they need more water.

My rule is "water when the mix feels crumbly-dry." That may mean twice a month, or it may mean every other day, depending on the time of year, temp, outside or inside, sunny or cloudy/rainy. If you always go by feel, it's hard to screw it up.

Denise in Omaha

"do your plants look dehydrated?"

That's somewhat tricky. I was under the impression that I don't really want to wait for them to get dehydrated looking, because by that point they'd already be too dry.

In any case, with the euphorbias it's easier to gauge since most of them either have leaves or tend to show dessication a bit quicker than the cacti do. Also they're all pretty much actively growing right now and being obvious about it, so I'm tending to give them a little more water.

It's harder to gauge the cacti, though.

In terms of the mix being crumbly/dry... It's a pretty light mix. It doesn't ever really compact to the point where it gets non-crumbly when wet, so perhaps it's a little TOO light or I have too many large particles in it or whatever. In terms of feel... the ones that are in clay I wait till the pot itself feels like it's not sweating out any moisture anymore, since it's hard to actually touch the soil itself given that the pots are fairly small and it's sort of hard to get through the spines.

Anyway, I wait till the pot stops sweating, wait a few days just to be sure it's dried, and then water. This leads to roughly a week between each watering.

Another reason I think I might not be watering enough is that the potting mix doesn't seem to hold a lot of water even when it is wet. Although perhaps this indicates, again, that I made it too light and might want to add a little bit of something water retaining to it.

I have watered my cactus once a week and longer in above 90 here in Texas and they are fine. I grow mostly cactus , opuntias. My succulents live more in the shade (bright light) and they get it once a week . maybe more if it gets close to 100. I am not good at schedules. This summer, I am more worried about too much rain.

I am sure there is a 'perfect' frequency at which to water each individual plant... but I have many dozens of plants in pots (well over 300) so I don't have the luxury of time to feel each one's soil. However I do find that most succulents are incredibly forgiving (obvious exceptions) and seem to do well no matter how often a feel like watering. I am off two days a week, so I water 2 days a week... but sometimes, particularly in the long summer days, I have opportunities to water more often so I do... sometimes every day to every other day. So far, with the few exceptions I did not specify above, 99% of my plants do great with whatever they get. Exceptions in the past have been plants in too much shade, or the super touchy things like Mesembs and caudiciforms. Those have to be set aside and watched a bit more closely. Thankfully, of the about 50 species of cacti I have in pots, none seem to care if they get watered once a day or once a month (some I neglect for months on end). I just notice that sometimes the ones getting more water flower more and grow faster. That's about it. I have had cacti sitting out of a pot for over a year (no soil, no water) and they still look fine (these are columnars or barrels... not small mammillarias). So with most plants, I think you can pick your own schedule and go with it... in most cases, as long as the soil drains well, they will manage. Just be sure you water watering them thoroughly when you do, especially if there is peat in the soil... peat soils often never get wet at all if you dont' water thoroughly and the plants do die of dehydration.

Of course all this is from someone living in a dry climate (southern California) that is fairly warm year round. Those growing stuff in humid climates might have to be a bit more careful I suppose.