If you are using Isle Evelup to train Pokemon when you have enough free time to do it the old-fashioned way, you are doing it wrong.
It's meant to be used when you don't have time to train them.
Each session of 30 Mins can net you ~300 Experience (At Lvl 3). With Beans, you can half that to ~300 Exp for 15 Mins. The Poke Pelago lets you do a max of 99 Sessions before you have to manually restart it.
So...
(99)x(~300) = ~29700 Exp Per 99 Sessions, which takes with Beans (((99)x(15))/60) = 24.75 Hours. Brilliant.
So then, how does that translate to an actual Pokemon. I'm going to use my Darmanitan for an example, since that's what I'm working on now, but of course that depends on the Pokemon (He's a medium-slow-ish exp grower). To go from Level 49-50 (the Min level for a viable competitive Pokemon), he needs 7,437 Exp. Not bad, he'll get more than 1 level out of doing this. So what about the next levels. 50-51 = 7,766 Exp. 51-52 = 8,103, 52-53 = 8,448. At this point, he's gone over the exp he'd get from doing this training. So he's getting 3 levels (almost 4) for sitting on his bum for ~25 hours. Not bad. But then, lets look at how what would happen if I did the physical work of leveling him up via battling.
Arguably, the Poni Gauntlet is the best location to level up Pokemon. Lets take for example one of the most common Pokes there, Pelipper. Defeating a level 58 Pelipper there (more or less the average level), will net me ~2000 Base Exp. Assuming I'm using the Exp Share along with the Luck Egg, he'll be getting 75% of the Exp., or ~1500 Exp per battle. Assuming you're using a Pokemon that can 0HKO everything at Poni Gauntlet, and that for some odd reason, you're very slow and only defeating Pokemon at a rate of 1 Per Minute,...
(29700)/(~1500) = ~19.8 Battles. In other words, in takes me about ~20 Minutes to do what it took Isle Evelup to do in 25 Hours. Of course, there are many factors that go into calculating how much and how fast a Pokemon grows, but in every scenario unless you're trying to do this while comatose, you're going to be
far faster than Isle Evelup in regards to leveling conventionally.
Sure, if you're going to say, stop playing Pokemon for a couple of days, then maybe you'll get more use out of it. Furthermore, Isle Evelup can do 18 Pokemon at once, while you can only realistically do 5 at once. But...
(20)x(4) = 4/3rds of an hour (you would need to do 4 sessions to do a total of 18 Pokemon, but you could just also go to 20), to do what Isle Evelup can do in 25 Hours. Still not really worth the effort. And who actually is working on 18 Pokemon at once?! At most, I'm working on 6-8, and usually I'm working on 4.
While the Isle Evelup level up function can work if you really don't have time for anything other than the bare necessities, more often than not if you have a fraction of time, you'd be better off just doing it the old fashioned way.