It depends on several factors. Is the CRM system integrated, the environment, how old is the current version we are upgrading from, etc. For clients upgrading from v2018 or earlier we typically take a copy of the CRM and apply the upgrades in a staging (test) environment before we upgrade your actual system.  Once the upgrades have been applied, we will schedule a training session to review the feature enhancements/advancements. Upgrades from v2019 and later are much easier to apply. Typically, these upgrades can be applied without any downtime.