There is no upper limit using time deposits at post office(at India).
Post-office time deposits can be open for:
1. one year
2. or two years
3. or three years
4. or five years.

Interest rates From Sat 01-Apr-2023 to Fri 30-06-2023 Period rates
1yr A/c	6.8%
2yr A/c	6.9%
3yr A/c	7.0?%
4yr A/c	Not available
5yr A/c	7.5 %

Assume that on Sun 21-May-2023 using online I am opening two TIME DEPOSIT:
1. Using 50000.00 INR as principal for 5 years.
2. Using 50000.00 INR as principal for 1 year.

PRINCIPAL	NUMBER OF YEARS	INTEREST	NUMBER OF YEARS	INTEREST	SAVINGS at POST ACCOUNT	OPEN TD FROM INTEREST
50000.00	05	20047.00 INR AFTER 05 years	00	00	00	00
			01	3488.00 from TD OF 50000.00	88.00	Open TIME DEPOSIT FOR 3400.00
			02	3488.00 from TD OF 50000.00 0237.00 from TD OF 03400.00 3813.00 = 3488.00 + 0237.00 + 88.00	13.00 = 3813.00 - 3800.00	Open TIME DEPOSIT FOR 3800.00
			03	3488.00 from TD OF 50000.00 0237.00 from TD OF 03400.00 0265.00 from TD OF 02800.00 4003.00 = 3488.00 + 0237.00 + 0265.00 + 13.00	03.00 = 4003.00 - 4000.00	Open TIME DEPOSIT FOR 4000.00
			04	3488.00 from TD OF 50000.00 0237.00 from TD OF 03400.00 0265.00 from TD OF 02800.00 0279.00 from TD OF 04000.00 4272.00 = 3488.00 + 0237.00 + 0265.00 + 0279.00 + 03.00	72.00 = 4272.00 - 4000.00	Open TIME DEPOSIT FOR 4200.00
			05	3488.00 from TD OF 50000.00 0237.00 from TD OF 03400.00 0265.00 from TD OF 02800.00 0279.00 from TD OF 04000.00 0293.00 from TD OF 04000.00 4634.00 = 3488.00 + 0237.00 + 0265.00 + 0279.00 + 0293.00 + 72.00	34.00	Open TIME DEPOSIT FOR 4600.00
			06	3488.00 from TD OF 50000.00 0237.00 from TD OF 03400.00 0265.00 from TD OF 02800.00 0279.00 from TD OF 04000.00 0293.00 from TD OF 04000.00 0321.00 from TD OF 04600.00 4917.00 = 3488.00 + 0237.00 + 0265.00 + 0279.00 + 0293.00 + 0321.00 34.00	74917.00 = 4917.00 + 3400.00 + 3800.00 + 4000.00 + 4200.00 + 4600.00 + 50000.00	Open TIME DEPOSIT FOR 4600.00

I agreen total investment and interest obtaining more money only after 6 years and not at 5 years
However, I can close the term deposit when ever I need after completing one year due to my emergency.
Also, 1 year term deposit wont help to save income tax at 80C division.
Example declartion using 80C division at income tax of india:
01. 99996.00 = 8333.00 * 12 for HRA(house rent allowance.
02. 80000.00 = School fees.
Here 179996.00(=80000.00 + 99996.00) is exceeding max amount(150000.00 INR) of 80C division of income tax.
Hence I feel to save money using any one of the following:
01. TIME DEPOSIT AT POST OFFICE
02. NSC AT POST OFFICE
03. MIS AT POST OFFICE
04. RECURRING DEPOSIT AT POST OFFICE USING MIS INTEREST.
05. MIS AT POST OFFICE USING MY MUM'S/FATHER's ACCOUNT
06. FIXED DEPOSIT AT SBI TO PAY: a. CURRENT BILL b. LIC (IF ANY) c. HRA d. SCHOOL/TUTION/SINGING CLASS FEES e. FUTURE TRAVELLING d. CLOSE ANY LOAN/INTEREST