Fix statistics retention default value.

60s * 60m * 24h * 31d * 12m * 5 != 5 years
60s * 60m * 365d * 5 != 5 years

But the second value is much closer then using 12 months with
31 days of which 4 months have 30 days and one has either 28
e.g. 3 days less or at best 29 days so 2 days less. When multiplied
with 5 years this mean you calculate something 30+ days to much.