I would reckon if the offers are not as good, then business must be better than it was, as they are not bothered about grabbing new business.
I send out offers on a weekly basis, and the quality if the offer depends on how busy my diary is.
Empty diary, cracking discount offer in a bid to fill it up.
Almost fully booked, not that great an offer as I'm not too bothered.
But I send them out every week regardless as people get used to seeing them and that's how direct marketing is done best (so I'm told)
And yeah, you're totally right about regular contact. It's called "conditioning". Back in the day, you used to have to make an average of 8 contacts to close a sale (for "sale" that could mean order, booking or whatever, but fundamentally is a sale). Nowadays due to information overload, it's something like 60, so yeah, you need to keep the contact up, hence CRC sending regular things out, even if they aren't amazing. It keeps you warm to them and keeps you opening their email.
Additionally, they will be classifying and datamining all email campaigns - I'd expect they have some very clever sub categories etc. From the email campaign they can track who opens the email, where they click through to, how long they stay on site, what else they look at etc. All of which is massively valuable data to an online business to plan sales activity and make more profit.