No one knows for sure when the time might come. Could be any hour. It is definitely a good idea to take one when you can and plan for what is inevitable eventually. Again, nobody plans to die but you should plan for a funeral when you can. It is not just going to be for you but for your loved ones as well. You'll help them to lessen the burden of arrangements that would have been otherwise hectic especially when they aren't really up for it.
I think, it's wise to take a plan ahead of time.
Someone's demise is painful, but the sympathy towards the deceased goes away when the burden of funeral surfaces. Death is uncertain. You never know when it could strike. Sometimes, it may not give you the time to prepare for the next. All of a sudden, it could come as a jolt to your loved ones. A funeral plan might come handy at such point of uncertainty. People after you will be relieved to know that they don't need to pay anything out of pocket, especially when the funeral arrangements are not so affordable. Afterwards, you'll forever remain in their good memories for not being a burden even in death.
You don't know exactly when you'll die. Maybe you'll live upto 120 years like my grandma. What I can suggest is, as long as the plan doesn't expire, then you can go ahead and make the plans so that you can make things easier as well. The only problem on planning funeral plans in future are financial constraints. Or maybe you can keep that money in the bank and make your children be aware of it. Starting plans now might sound very weird especially to lots of people and they'll start thinking about lots of things and even think that you're about to die.