There have already been times when it wasn't enough and people's transactions were delayed for days.
Multibit classic isn't being actively developed any more. I recommend switching to electrum. If you don't switch and find in the future a time when the maximum fee isn't enough to move your coins you can use these instructions to export your private keys from multibit, then either import or sweep them into electrum.
Start multibit, select the wallet containing your coins, then click "tools", then select "export private keys" as shown in the screenshot.
A new tab should open like the one below. Select "do not password protect export file" at the bottom of the window, then click the "export private keys button".
Click the windows start button, then copy and paste the line of text below into the search box that appears, then press the enter key to open the hidden folder containing your multibit wallet files.
%appdata%\Multibit
This is what your search box should look like after you have copied and pasted the line above into it.
Inside the folder that opens there should be a file with an extension ending in ".key". Open it in notepad and copy your wallet's private key. In the example file below the private key is the bit in red.
# KEEP YOUR PRIVATE KEYS SAFE !
# Anyone who can read this file can spend your bitcoin.
#
# Format:
# <Base58 encoded private key>[<whitespace>[<key createdAt>]]
#
# The Base58 encoded private keys are the same format as
# produced by the Satoshi client/ sipa dumpprivkey utility.
#
# Key createdAt is in UTC format as specified by ISO 8601
# e.g: 2011-12-31T16:42:00Z . The century, 'T' and 'Z' are mandatory
#
KwUVsx4nd4UTHUtNTPnLEEqapCFvNiBrVASBZPa1ZvStQbUD87VK 2017-03-26T01:36:45Z
# End of private keys
After you get your private keys you can use these instructions to import them into electrum.
http://docs.electrum.org/en/latest/faq.html#can-i-import-private-keys-from-other-bitcoin-clientshttp://docs.electrum.org/en/latest/faq.html#can-i-sweep-private-keys-from-other-bitcoin-clients
