We are generally invited to fly Va+10 for Flaps 15 or Va+5 (due to the increased tailstrike risk) for Flaps 35, both in non-icing conditions. In icing, it is Va-ICE without any increments.
Although an approach at Va is allowed under most circumstances and may be more desirable under some, the increase will add some energy to the aircraft, allowing for a smoother roundout and less risk of tailstrike. With Flaps 35, this is obviously a trade-in for an increased risk of a nose wheel landing.
Increments for wind speed are at pilots discretion. Va + 1/3 wind or gusts (whichever is higher), up to a maximum of 20kts increment and not exceeding Va-ICE is the general rule.
Of course, the LDA requirements need to be minded when increasing speeds. An increment of 10kts will increase required distance by 14%; 20kts will increase the LDR by 25% on top of all other factors. So speed increments are always subject to careful selection and very much dependent on the general situation.