I don't have an official answer because I do not work for Symantec. It might have to wait for someone with Symantec to respond and you may receive a quicker answer if you contact your account representative. However, looking at the page below, on the right, you're able to see the End of Life dates for Patch Management. If you look at 7.1.2 (the version prior to 7.5), it shows an End of Engineering Support date which was the same as the End of Life Support date. Version 7.5.1 does have an End of Life Support date associated with it so I would think that you would receive patch imports up to that date. Please keep in mind that this is speculation and like I stated before, you'll either have to wait for someone in Symantec to respond or contact your rep.
https://support.symantec.com/en_US/patch-management-solution-for-windows.html