Plan to have the Engagement Manager travel to the outsource locale every six months, at least. If you’re having any type of persistent problem, the engagement manager must make a visit to the site as soon as feasible.
For offshore locations, plan to have at least one of the the senior technical people stay in the US for at least one month. If the team has more than one technical lead, you should plan to have them stay in the US for a month, too. Rather than having them all travel together you may want to stagger them. This will help you budget and will allow them to tack back snapshots of what’s going on with the US team several times a year.