If you elect to upgrade to the SUP2T check your line cards are compatible.
http://www.cisco.com/c/en/us/products/collateral/interfaces-modules/catalyst-6500-series-supervisor-engine-2t/data_sheet_c78-648214.html
Which SUP720 do you have? I can't see Feb 2017 listed.
The SUP720-3B goes end of support 2018 http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-series-switches/eol_c51-697975.html
A bunch of 67xx linecards and SUP 720-10G-3C go end of support 2020 http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-series-switches/eos-eol-notice-c51-733297.html
End of support is the last day any support is available. You may find 3rd party support.