If you're using windows try this:
1. find where you have bitcoin core installed
2. locate the .exe file of your wallet
3. Create a shortcut to it
4. Right click the shortcut
5. properties
6. add -checkblocks=10 after the directory it's being ran from.
Now you can add the shortcut to your desktop. Every time you open the wallet using the shortcut it will start faster since it won't have to do the default check of 288.
Or your add it to the startup folder (C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup) if you want. Adding it to the startup folder will start your wallet as soon as you open your computer.
It helped me reduce the wallet's start time from minutes to seconds. I don't know if there's something to reduce it's closing time though. It was never much for me anyway.