I've been through this, a few years back when our DSL took a hit and I had to keep our connectivity up anyway.
Living with a slow 56k modem link between your LAN and the Internet will:
- give you a reversible foretaste of what you're planning. Don't like dialup? You'll hate cold-turkey so much that you might not be at all productive.
- highlight your Internet time-waster habits, because the waits for those pages to load will become obvious. This is called "rubbing your nose in it". For anything that's not essential, you *will* find better things to do, or more efficient variants on the familiar. Setting your mail-lists to daily-digest, for instance.
- make it obvious what Internet resources you'll have difficulty doing without. Keep a log of the ones you keep going back to anyway: they're your reasons not to give it all up.
- change some of your Internet habits right there, because there is no instant gratification, instead you have to wait for everything to finishing downloading. You can dovetail some tasks into those waits, such as, getting a cup of coffee while Google News loads, or doing the laundry while waiting for all the new-format Slashdot comments to be visible, or going shopping while a YouTube video is being sucked in for local replay. You'll get impatient and get off your ass just to keep some momentum going because the Internet isn't doing it for you anymore.
You'll get used to prefetching bulky things you really want on hand, and using LAN storage to make it available for browsing. wget will get a lot of scripted use, particularly the "wget -c" option, because it can take most of week to get a CD ISO in. You'll learn to use local tooling to replace online stuff that isn't always there. Early on, for example, I set up a local wiki and a web calendar, to be visible to every machine on the LAN. Then I wrote CGI tooling to fill in my specific blanks. YMMV.
You will likely do a lot of scripting to automate fetching in things you really want or really need, and transferring out your responses. A cron'd mail-check every 5 minutes will keep up a dialup link that idles-out in 15 minutes. This might include bringing the link up in the wee hours to do downloads when nobody's likely to phone, and dropping it again, ready or not, when the phone line needs to have a phone ready for use.
Dialup will have you looking at your computer less as a source of consumed entertainment and more as a creative workspace. If that's what you're after, dropping to 56k might be enough.