FAQS - REPLACING OLD WITH NEW OR 2ND HAND
HOW OFTEN DO I NEED TO REPLACE?
It depends upon many factors: what device are we talking, which manufacture, and the specifications at the time you bought originally.
Take an Android mobile: 2-3years - as updates will stop after this time. An Apple mobile - new model: 4-5years as updates will keep coming - BUT the batteries are not known for lasting, so you might still want to upgrade in 3-4 years.
A PC or a Mac is a different animal, and people usually keep these devices for a long time, but only if the specifications were right when you bought. Buy cheap and slow, it's only going to get worse.
WHAT DO I NEED TO THINK ABOUT?
When changing from one system to a new one, even if you are staying with the same type or manufacturer or ecosystem, you need to think about these things: Is my data backed up and in a format that is right for use on new system. Have I got all my account credentials, passwords, activation codes, software or app install programs? If you use POP email, you need to back up your .PST files, and other useful files from your system data area. Never get rid of your old system until you are fully up and running with the new, that way if you forgot something, you can get it. (Note that is why I prefer to replace hard drives in computers with new, rather than reinstalling, you always have a backup, also it probably needs a new one.
DATA BACKUP AND DATA SYNCING
This has been said this lots of times elsewhere on this website, but here it is again - you must backup your data. You also must sync your data to another location. What is the difference? one is protecting you all the time if a device fails or you lose it. The other is a snap shot of your data at a specific time, which protects you from viruses and malware. You must and should be doing both which makes moving to another device that much easier and quicker.
If you don't like online backup or syncing locations then invest in a Network attached storage device and create your own personal cloud location. Which is great, but the others are much easier.
ECO-SYSTEM CONVERSION
Very do able, as far as process and what you are able to achieve, but something never to be taken lightly. You have to really want it, as if you have been in one eco-system for a long time, you will have potential a large amount of money invested in content within that eco-system, movies, films, games, and apps.
Then there is the learning curve, and no matter which eco-system you are a part of, e.g. Apple, Android, Microsoft, etc there will be things that they do really well, better than the rest, and you will miss those things. So, you need a really good reason to change over.
If you don't buy content, then contacts, texts, emails, most app data can be exchanged between eco-systems without too much issue or trouble, and applications on a computer can help with mobile transitions. It is also easier to go android to apple as there are iTunes apps for play store content like movies, but not a matching movie player for Apple movies on your Android.