When loading a template database, it may depend on the storage location, how fast the operation will be finished. If one accesses e.g. a global template database over the network, there will be a greater delay than loading from a personal tamplate database typically hosted on a local drive.
In the Online Help you may find additional informations on tuning the performance in the chapters Data Management > Project Database > Working with Project Databases > Optimizing FlexPro for Large Volumes of Data and … > Troubleshooting Project Databases.
When using a specific project database a long time, the space used on the storage will increment even if one deletes a lot of datasets and other objects; using the defragmentation can shrink the size to the amount actually needed. The Online Help chapter Data Management > Project Database > Working with Project Databases > Defragmenting a Project Database describes the operation.