It depends on the type of surface "dressing" you want to use, the level of traffic, the type of traffic, weather, materials availability and other factors. You have not provided much information, so this will all be very general.
The most common surface dressing is a "chip seal", either in single application or double application. These work quite well, provide additional usability for the wearing course, and increase skid resistance. They do not correct structural problems with the pavement and will provide no real structural help to the pavement. They are coarse, noisy and flying gravel is a problems, but for low volume, low speed roadways, they are good.
Microsurfacing is similar but a more meticulously applied, finer graded aggregate.
As Ron mentions, we have limited information so it is difficult to give a complete answer. However, I'm sure you are talking about something that falls under the general category of "Pavement Preservation Strategies (some good terms to google)." Most pavement preservation strategies should be good for about 5 years or more IF, 1) The proper pavement preservation strategy is selected for the given road and it is applied at the right time. 2) The selected strategy must be properly constructed or applied.
The starting point for use of any preservation strategy is a thorough investigation of the current condition of the roadway and failure in this regard is overwhelmingly the primary reason for premature failure. Preservation strategies do not solve structural problems so as a prerequisite before employing any of them, the road must be determined to be structurally sound. No pavement preservation strategy will last 5 years on a structurally failing road, not matter how well it is constructed. Any areas that are not structurally sound require reconstruction before any preservation strategy is employed. Ideally, the roads structural condition would be investigated using a falling weight deflectometer. Practically, this equipment is not always available and may be costly so visual inspection of the pavement to determine types and degree of pavement distress is utilized, both for structural evaluation as well as other pavement distresses. Some sure signs of structural failure are potholes, severe alligator cracking, wheel path longitudinal cracking and unstable rutting. Any of these are disqualifies the road for any kind of preventive maintenance strategy unless the areas are small enough so that spot repairs can be used to restore the road structure in those locations only. If possible, I strongly suggest obtaining a copy of Distress Identification Manual for the Long-Term Pavement Performance Program,, U.S. Federal Highway Administration Publication No. FHWA-RD-03-031. The 150 page book contains clear color photos of 133 different pavement distresses and is very helpful for evaluating the kind and severity of nearly any kind of pavement distress, both for flexible and rigid pavements.
So, can you give a description of the present road condition? And, can you describe the kind of surface treatment you are referring to by the term, "surface dressing?" Also, anticipating where this thread is likely to go next after you provide the needed information, are polymerized asphalt emulsions available in your locality?
