We have discovered (through the diligent work of one of our users – Thanks Nate) that you can have so many active calls that it interferes with the ability to log-in on the mobile apps.
How many active calls can you have before it causes problems – that depends. Early investigations suggest the problem arises from a combination of response time from the server and maybe some caching in the app – both of which are being worked on. For our users that routinely recycle calls – using a search of the archives to create a new call – it is a much lower number. If you have calls that have hundreds of call action entries the interwebs and your cellular carrier will likely make reloading your call logs a sluggish endeavor when you have a few dozen calls. On our test systems where we usually only have a few dozen call actions per call we have loaded hundreds of calls before we witness much of a slow down. We still haven’t been able to recreate the login failure that poor Nate discovered, but we know he was able to fix it by reducing the number of days before calls are archived.
The archival days setting is available under the drop-down the includes your name in the upper right hand side of the screen. Select the Profile and Call settings screen.

You will want to adjust the setting labelled Completed calls archived (days)! This can be set between 1 and 365 days and impacts how many Completed calls are kept in the current windows. The calls are never lost, but the Archived calls are not pulled into the browser until you select the Archive tab. Long time users can have tens of thousands of calls in the Archive tab. More about this can be found in the CallPlease Speed and Tuning note.