> I'm curious how long these companies can have losses.

Parent didn't ask about access to credit or market capitalization rates, they asked how long they can burn for. If you no longer need credit because you're profitable, then keeping your asset value up is moot.

So yes it very much is an optional spend. I welcome you to listen to a podcast by the CFO of NetSuite:

https://a16z.com/2015/05/15/a16z-podcast-why-saas-revenue-is...

NetSuite's most profitable year was...2009. Yes that 2009. They basically turned off S&M when the economy crashed.