Is it advisable to place an exhaust fan at roof eves to have better ventilation between the roof and ceiling?

Over the years in the building industry it has come to be known that proper attic ventilation is key to long roof life as well as reduced costs for heating/cooling your home. We used to just put vents on the “gable’ end walls close to roof level. The Gable is the side of your house above your highest living floor that forms the “peak” or “A” frame if you have a pitched roof. While that did afford some air flow, it was usually concentrated only around 5% of space near the vent. After many years of research it is found that proper ventilation requires both “intake” and “exhaust” Your goal is to create positive airflow along entire area of interior attic space. The way that air flows against your house is this:
As air rushes against the outside walls, it travels upwards and over the roof. Have you ever seen a wind tunnel demonstration on a wing or other surface? The proper and most effective way to create proper flow is to install vents along the “eaves” or “soffits” aprox. every 3- 4 feet. This is the area under the overhang along your long walls. (usually below where gutters are installed) Be sure to clime into your attic and squeeze down to the area over these vents and remove the insulation that could be covering them or your efforts will be negated. Also, there is a product called “rafter vents” that are poly or foam channels approx 3 ft long that will fit between your rafters. You install these by just sliding them down between the rafters to the eaves and vent locations and they will keep the air flow clear of insulation and debris.
For “exhaust” the best is a continious “ridge vent” . This will allow air to flow over entire “under-roof” surface. The ridge vent installs by removing the covering or “shingles” from the very top or “peak” of your roof. Cut the roof sheathing (plywood or ridge board) 1 1/2″ to 2″ down along entire lentgh or roof “peak” stopping your cut about 1 foot from the ends. Then purchase one of many “ridge-vent” styles available. Enough to cover this cut you just made. Some are plastic typr mesh that comes in a roll. You simply roll it out over the cut and nail it into you roof sheathing using 3″ roofing nails. Others come in 4-8 foot sections but install the same way. You then install new “ridge” or “cap” shingles directly over this product using again, 3 inch roofing nails. Be carefull not to nail them to tight and smash the vent material. You need to maintain the opening of about 1 inch along the entire run for it to be effective. Also there is an aluminum version that comes in 8 – 10 foot sections that gets nailed down with 1 1/2″ roofing nails and does not require any further covering. Just be sure to by the connectors and end plugs and some silicone to cover the new nails. This product comes in white, brown, and black. But can also be painted.
The second best exhaust option is a thermostacically controlled attic fan. This will require a bit of electrical wiring. You should locate this fan as high in the attic as possible. If only 1 is used then locate it in the center of the area but still as close to the peak as possible.
Your goal is to keep the underside of your roof sheathing close to the same temperature as the outside but with positive airflow.
While the attic fan is a positive addition. Like the old gable vents, it will localize the airflow.