When a profile is more than 90 days old and the average of the last five startups is more than 20 seconds, a user will see a notice with buttons to either permanently ignore the warning or "Learn Hot to Speed It Up." The latter directs the user to the SUMO page to refresh their profile.
 Configurable via pref
A profile refresh is a high friction recommendation to address slow startups that is potentially harmful to the user's experience. Furthermore, we don't have confidence that it will address the cause of the slow startup. For example, for users on older systems a "slow" startup may be normal. Alternately, if the user has third party software performing DLL-injection which slows down startup, a profile refresh will not help. Additional discussion in this deck.
No notice is shown to users when their startup is "slow." Other initiatives will address the real and perceived performance of slower startups.