The correct answer will be it depends. However, speaking generally, the time frame for ICA to process PR applications on average in Singapore for PR applicants will be around four to six months from the time you submit your application. If you are confused about applying for permanent residence, you can get an immigration consulting agency to help you improve your Singapore permanent residency approval chances too. Do not waste unnecessary time waiting, as there is no guarantee that the faster or longer ICA takes to reply you is any indication of approval or not. Additionally, once you have gotten your own permanent residence status approved, you can also apply LTVP for your parents. So you want to get your Singapore permanent residence approved right from the start as fast as possible
There are several factors which can affect the length of this processing time for you.
First of all, the above time frame of four to six months for Singapore PR application processing time is actually for those who have submitted their documents perfectly, and are well qualified to get a permanent residency. In other words, this time frame is for those who were always going to get approved. It only requires this period of time due to massive amounts of PR applications that the Immigration Checkpoint Authority ICA of Singapore has to process yearly.
If you do not have document proof of one of more your claims in your permanent residence application, it will be likely delayed, and additionally, potentially even rejected. It is so important for you to be able, and to provide document and proof backing up the information that you input when you are applying. If you are unsure about what documents to prepare, then please read my experience applying for a Singapore PR here first. Get those documents ready before you apply.
ICA will be biased towards approving candidates who are clearly well qualified to be a Singapore permanent resident. For instance, if you have stellar academic record with prestigious universities, make great income and are perhaps even a grassroots leader or at least a volunteer, your PR status will likely get approved ahead of others, as there is no question about your application. However, if you are a weaker candidate due to your credentials, then it will very likely take longer than four to six months. Sometimes, it can take up to one to two years before you will hear back from ICA, and even then there is no guarantee it will be an approval. Therefore, it is so important to improve and work on the necessary from day one.