We don't use this functionality unless direly pressed, for this reason (limited number of fields).
Like Madalyn, I'd advise you to audit your fields and determine whether the tracked fields are:
1) really being used that much (e.g. are they on deactivated fields? are they being used once a year? Is the working team really using the information as much as they promised you that they would?) and
2) whether or not there are any other alternative solutions. (how are they using this information? what do they need it for? how are they looking it up? Is there a better way?) Many admins might opt for calculated fields which write similar historical record information to the custom form rather than to the update stream, as an example.
On a side note: @Doug_Den_Hoed__AtAppStore -- I don't know if your health checking app looks at the update feed information (/setup/update-feeds) at all, but this wasn't on my radar for our internal checks so now I am happy to put one more thing on the admin maintenance list to keep up to date. That said, in an instance with 131 active workflows, we have 130 custom form fields being tracked and I've never checked to see which fields are actively being used so this number will probably reduce shortly. Additional note to self - check to make sure that if I delete a field, it removes itself from this page.