Benchmarks for Lead Lifecycle Conversions

Can anyone share benchmark data for the lead lifecycle for a B2B services company? Percentage of Prospects to MQLs, MQLs to SQLs, SQLs to Opportunities, Opportunities to New Customers?

I have some old data from Marketo percentage of prospects to nurture = 73%, Nurture to leads = 3.5% per month, leads to opportunities = 16%, opportunities to new customers = 33%. Is this a good starting point or too high or too low for out of the gate expectations?

Any direction is much appreciated!