If you are using 'side cars' 'expension modules' or any other device that displays presence using sip subscriptions and are running an asterisk 1.6.x.x branch of asterisk, you may want to avoid reloads until after hours. At least until a fix is released.
https://issues.asterisk.org/view.php?id=16093
It appears that reload has an undesired effect of flushing the subscription table which means the phones wont display presence until they re-subscribe some time later.