This chapter first discusses the problems that arise when applying general principles of contract law to the way in which long-term contracts are regulated and then presents an alternative approach – ‘Relational Contract Theory’ (RCT) – that focuses on the parties’ relationship during the term of the contract. The case study chosen for this purpose examines two social long-term contracts: prenuptial agreements and residential tenancy agreements. I will argue that the three general principles of contract law are ill suited to regulate these types of long-term contracts and that more attention should be paid to the parties’ evolving relationship. This is a more suitable approach, given the RCT’s focus on the parties’ relationship, rather than on the ‘black and white’ letter of the contract itself, which conforms to Point 6 of the European Social Contracts Group Declaration (‘EuSoCo Declaration’), which states that the law “should be able to cope with long-term relational problems of changes in human lives instead of providing only remedies typical of spot contracts.”