In October Conference 2000, Elder Oaks stated that "The commandments, ordinances, and covenants of the gospel are not a list of deposits required to be made in some heavenly account." He was explaining that more important than what we accumulate or have is what we actually become. However, I believe his analogy also carries forward to imply that there is no straight, temporal quid pro quo in the gospel. It is not a bank account where we store up good works that equal a certain sum of blessings to be withdrawn when needed. By which I mean, if you pay your tithing you can’t always expect that mystery check to arrive the very next day.
Yes, we can store of spiritual strength for times of trials–we can build a spiritual reserve to help us in our lives. What we cannot do is commit a certain act and expect or demand an exact specified blessing. Where this pseudo-doctrine is most often taught is through tithing and the Word of Wisdom. We often hear that if we pay our tithing we will be monetarily blessed–often this is taught that we will never want. In the case of the Word of Wisdom it is taught that if we live it we will always be healthy.
The root of this pseudo-doctrine is often conjured through D&C 130:20: "There is a law irrevocably decreed in heaven before the foundations of this world, upon which all blessings are predicated and when we obtain any blessing from God it is by obedience to that law upon which it is predicated." We often read this to mean that for every act there is an exact blessing assigned. First, this seems intuitively incorrect. There are no good examples of gospel laws for which the obedient always receive the same blessing. Both Job and Christ often received tribulation and physical strife in place of certain temporal blessings. Which brings us to the second point: we desire to place this scripture within the context of temporal, physical blessings. Of course, what Christ and Job have in common is the teleological result: both receive exaltation. The scripture does not indicate any quid pro quo. It merely indicates that living the laws of God brings blessings. It does not indicate whether these blessings will be realized in mortality or whether every law brings an exact specified blessing in tow.
In the case of the Word of Wisdom, many who adhere to the WoW (as currently constituted as a ban on certain substances) end up getting very sick or having chronic bad health. Many who live the law of tithing suffer enormous financial setbacks from which they never recover. I am not saying that there are not times when we receive that unexpected check in the mail after paying our tithing in faith (knowing it will mean no groceries next week). Or that we do not experience health benefits from living the WoW. I am stating that living the commandments only brings ONE guarantee: reception of the grace of Christ and opportunity to use the Atonement to receive forgiveness. This guarantee brings with it the peace of the Spirit and a blessing that exaltation is possible. It does not bring with it a promise of good finances or robust health.
If we desire a guarantee, best to invest our money in a low risk manner–such as government bonds (or never fill a bank account above the FDIC insured amount). Temporal guarantees in the gospel, however, seem in very short order. After all, the gospel is an eternal endeavor with eternal goals.