It depends on your threat model. If you don't run any untrusted code on your hardware (including Javascript), you can safely disable the mitigations. If you do run untrusted code, keep them enabled.
Is there an example in the wild of a spectre exploit stealing my gmail cookie and doing something with it? (Would be difficult since it's tied to other fingerprints like my IP)
Or stealing credit card numbers when they're in memory after I place an online order?
For regular end-user desktop machines, the mitigations only decrease performance for no real benefit. Spectre is a highly targeted attack, it's not something you can just point at any random machine to retrieve all their bank passwords or whatever.