I have noticed the site performance depends on the number of users.

When it is morning-daytime for me (India), the number of online users hardly touches 450-600. At this time, I don't see the 'heavily loaded... upgrading soon' very often. Perhaps 1 or 2 times out of every 10 times.

When it is late evening-night in India the number of online users touch 800-900. At this point, if I access the site, I get to see the 'heavily loaded...upgrading soon' very frequently. Something like 8-9 times out of 10 times that I try to access.

PS. This is only an observation based on what I have seen the last 3-4 days.