Well ... when you say "perpetually" that isn't likely since your transition between employment and retirement only occurs once. As other have stated, legislative change to tax rates is unpredictable.
To get to details: Assuming you have sufficient "earned" income (not pension) to qualify to contribute and don't exceed the limiting AGI thresholds for contributions ... Consider the real impact of your plan. Calculating the absolute dollar value is simple. It is ((tax rate while employed) - (tax rate while retired)) x $6500. So, if contribute the maximum of $6500 and you are in the 25% bracket while employed, then you fall to the 15% tax bracket when retired, the saving is only $650. Remember that if you experience any earnings in the account before your withdrawal, that will be additional income on which you will owe tax.
