Vicidial itself isnt culprit in this case .. it depends on many factors like mysql / asterisk ( meetme plus ztdummy =

) . I recommend you atleast run a script at some time in a day that should ..
1) Stop and start asterisk
2) run AST_mysql_vars_clear.pl script ( name is lil different i think ) .
3) Restart httpd
4) Restart mysqld
step 3 and 4 arent really needed .. Mysql and apache are good enough to work for long run . Restarting asterisk once a day is a good idea always

and second script logs out everyone and clears temporary data in database so it almost always helps when you have a random problem like agents getting multiple calls or 2 agents in same conference or something like that .
Run this job via cron when nobody is using the system and i am sure it will work great for a long uptime .
( In worst meetme errors case you can stop asterisk unload all zaptel modules from kernel ... reload them and start asterisk .. this also helps )