I have a Montegue as well and also use a mix of beads and an Oasis. During the spring/summer/fall I can go months and months without needing to refill my Oasis. During the winter (with the lower RH in the house) I fill it much more frequently...maybe every three weeks or so. I like using the combination of media as I think the Oasis kind of automatically recharges the beads.
I prefer my RH 65% or lower, but YMMV. If you end up using the 70% beads, it may help achieve acceptable RH during the winter, but it could also cause higher than desired RH during the summer (meaning 65-70 in the winter, 70, maybe 70-72 in the summer). But if you prefer 70% it should be fine.
I will have to look into sealing my humidor a little better as Eric suggested. Maybe a New Year’s weekend project.