Note that the input voltage offset (due to input circuit imbalance), which for a specific physical device (a single one) varies mostly with temperature, is only one of the non-ideal characteristics that are modeled as an input voltage at the input pins.

Does it vary with time or supply voltage etc?

Power supply rejection ratio can also be modeled as a variable input voltage offset, so yes (indirectly).

Common mode voltage gain is another example, as well as imbalance caused by offset current through large input resistances (even the polarity may change close to the rails).

For a specific model all these contributions add to the equation shown in the question, but they may differ by an order of magnitude or more. Which means that, without significant temperature variation, a software compensation (or even an external imbalance compensation with resistors) may be enough for the application requirements.

Note that the input voltage offset (due to input circuit imbalance), which for a specific physical device (a single one) varies mostly with temperature, is only one of the non-ideal characteristics that are modeled as an input voltage at the input pins.

Does it vary with time or supply voltage etc?

Power supply rejection ratio can also be modeled as a variable input voltage offset, so yes (indirectly).

Common mode voltage gain is another example, as well as imbalance caused by offset current through large input resistances (even the polarity may change close to the rails).

For a specific model all these contributions add to the equation shown in the question, but they may differ by an order of magnitude or more. Which means that, without significant temperature variation, a software compensation (or even an external imbalance compensation with resistors) may be enough for the application requirements.

Thanks to @SpehroPefhany's contribution I can provide a graphical representation of what I mean about how two sources of voltage offset can be relatively compared:

Note that the input voltage offset, which for a specific physical device (a single one) varies mostly with temperature, is only one of the non-ideal characteristics that are modeled as an input voltage at the input pins.

Does it vary with time or supply voltage etc?

Power supply rejection ratio can also be modeled as a variable input voltage offset, so yes.

Common mode voltage gain is another example, as well as imbalance caused by offset current through large input resistances.

Note that the input voltage offset (due to input circuit imbalance), which for a specific physical device (a single one) varies mostly with temperature, is only one of the non-ideal characteristics that are modeled as an input voltage at the input pins.

Does it vary with time or supply voltage etc?

Power supply rejection ratio can also be modeled as a variable input voltage offset, so yes (indirectly).

Common mode voltage gain is another example, as well as imbalance caused by offset current through large input resistances (even the polarity may change close to the rails).

For a specific model all these contributions add to the equation shown in the question, but they may differ by an order of magnitude or more. Which means that, without significant temperature variation, a software compensation (or even an external imbalance compensation with resistors) may be enough for the application requirements.