The word translated from the Greek as dispensation is accorded this definition in the Strong's concordance:Paul was a dispensationalist, so your opinion is incorrect (though very common).
Eph 3:1-7 (AKJV/PCE)(3:1) For this cause I Paul, the prisoner of Jesus Christ for you Gentiles, (3:2) If ye have heard of the dispensation of the grace of God which is given me to you-ward: (3:3) How that by revelation he made known unto me the mystery; (as I wrote afore in few words, (3:4) Whereby, when ye read, ye may understand my knowledge in the mystery of Christ) (3:5) Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit; (3:6) That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel: (3:7) Whereof I was made a minister, according to the gift of the grace of God given unto me by the effectual working of his power.
3622. oikonomia oy-kon-om-ee'-ah from 3623; administration (of a household or estate); specially, a (religious) "economy":--dispensation, stewardship.
Said another way it's an office that carries with it the authority and responsibility to see to it's accomplishment. Paul was so charged and it is this of which he spoke. It is not indicative of period of time by definition but can be said to be in that it covers that period of time that one can avail themselves of the gift of grace through faith. That limited time offer ends at the return of Christ It appears that this word has taken on a much broader definition as the result of its usage in conjunction with Dispensationalist doctrine.