i won my first 2 with FOS. The next 2 took 3 months to be assigned and then declined straight away as they believe I raised too many chargebacks on Revolut so Revolut are well in their rights to decline
It took about probably 70 days. Yes they challenged the dispute just a few days before the 40 days and I don't know what evidence they sent revoult but within a few hours revoult had challenged their evidence and I won the dispute a month after that