Google described Lollipop as the biggest update to Android ever and if the latest rumors surrounding its successor prove accurate, the search giant may have to go back to the well once again.

Sources familiar with the matter recently told Android Police that Google is planning to implement a hard cut-off date for Nexus device update support to go along with Android M. Specifically, Nexus devices will get major system updates for two years and security patches for three years following an operating system's release.

Alternatively, we're told that security updates will be guaranteed for at least 18 months from the date of purchase in the Play Store (whichever is longer).

If true, this would put an end to the uncertainty surrounding device updates. Furthermore, it'd also give potential buyers yet another reason to opt for a Nexus device (assuming the lure of a pure Android experience wasn't enough).

It's worth mentioning that these rules would apply to both new and older Nexus devices but not all. The Nexus 4, Nexus 10 and Nexus 7 (2012) won't be getting Android M and thus, won't be part of the major update guarantee although security patches will still be offered based on device release date for a bit longer.

Google's annual developer conference kicks off later this week. Most expect the company to unveil its next mobile OS - Android M (codenamed Macadamia) - but it's unclear if the Nexus update guidelines will be announced simultaneously.